Is she hallucinating 

(reflexive doubt more than reasoned counterargument) Probably not? At least not in a way where "Merrin is experiencing hallucinations" is an explanation for this and not for everything else since the moment her experience departed the realm of how she expected Reality to work, and she had already concluded that it made sense to make decisions as though the whole being on an exoplanet thing was real and not a hallucination, and her own internal probabilitymass-assignment to it is not that high at this point since hallucinations are not known for having such coherent laws of physics and biology. She's just being lazy in coming up with hypotheses here. 

Oh no he's still there, she thought he was done, is this just her life now 

Her life is quite interesting! And Laeirthe prefers existing over not-existing. Quite strongly, actually! He's here - for some definition of 'here' and 'he is', at least - and she seems to need some advice. 

...And this part is especially interesting. Whaaaat if 'Estha' can do economicmagic transport-portals to other planets from here, and decided to surprise her with a food delivery? That's very intriguing! 

....Merrin is so dubious of the spontaneously-appearing food! She will go pick up a piece and try to break a bit off and rub it between her fingers and sniff it to figure out what it's made of. What if 'Estha' is an alien shapeshifter doing a questionable job of imitating her boyfriend and faking human physiology, and since he's an alien he delivered food she can't even eat

It's bland bread, with a slightly crispy yet still bland surface, surrounding a bland omelet of bland cheese mixed with bland vegetables, like a sort of bland burrito with no outer cracks, or a huge bland pastry bun with an apparently solid exterior!  Though if Merrin only broke off a sufficiently little bit, she'll just get the outer bland bread part.

(Magical food can still dry up if you leave it out, so Esta made it in a form factor that put the moist parts inside.)

(Merrin will eventually break off a large enough piece to determine that there's an interior with protein and vegetables.) 

...She has so many additional questions. 

Also it feels really socially awkward to wake Estha and ask him to explain where and how he obtained the food? He's probably going to calmly inform her that her mind was edited and she's just forgotten some totally normal method for obtaining food, and she will feel like a fool, and also what if she's WRONG that he's pretending to be asleep and she rudely wakes him up? Or what if she's right and he guesses that she noticed and it would've been better if he didn't guess that she noticed? 

- she catches that thought BEFORE the internal voice of Laeirthe from her fanfiction says something brutally harsh about how stupid that is. 

...It's almost 06:00, anyway, he hasn't had a shortage of sleep. (Also it is, as expected for this time, now just below freezing even inside the shelter. Merrin would usually get up briefly and then go right back into her sleeping pod.) 

Carrying one of the breads, she goes over to the sleeping bag on the floor, squats down (ooooof the delayed onset muscle soreness, that's mostly on her for not EATING ENOUGH PROTEIN after yesterday's exertions) and clears her throat, quietly enough that if he really were exhausted and deeply asleep it probably wouldn't disturb him? 

He opens his eyes fully, and says in very heavily accented, memorized Baseline, "Time for us both to wake for the day?  Answer simply."

.....His language function got worse again??? 

Concerns! Questions! Suspicions! 

Well, Merrin isn't getting back to sleep, between her two sleep blocks she's gotten ten hours – normally she would have her ten hours earlier in the night and be awake for six hours and then still get another few hours before dawn, but she's probably not going to be sleepy enough before dawn anyway. And he doesn't look like someone who's unhappily forcing his eyes open despite still being exhausted, she doesn't think? 

"Yes," she says in Baseline. 

He sits up enough to remove his hands from the sleeping bag, and touch the pentagram now once more around his neck.

Tongues.

And since he only had two of Tongues, he'll use it now, while he speaks her language.

Cultural Adaptation.

(Esta is not particularly trying to conceal either the gestures or the spellwords, over those next twelve seconds.)

Yesterday Merrin had higher priorities, and was also exhausted and running extremely low on metacognition to spare for anything except 'tracking whether she was still capable of providing medical care'. 

Today, she does more consciously note the weird not-words - or not Baseline words - he's saying, timed to coincide with the weird gestures. 

...Might as well not bother hiding that she's confused, she isn't trying to pretend to be exactly like the person Estha thinks he remembers her being because that sounds frustrating and impossible.

(To the extent that Merrin can deliberately control her facial expressions, which to be clear is much less than what is expected of Chelish people, she'll let 'confused' be loudest, to try to conceal the 'suspicious paranoia' part. It's actually a lot easier given that the suspicious-paranoia part is living in an imaginary fictional character who is not in control of her body or facial expressions.) 

He speaks again.  His Baseline now sounds more natural and idiomatic than before, though not quite like Estha; more like one of her superiors in Exception Handling speaking to her.

"It seems quite cold now.  How have you been surviving the cold, and the heat?  When is it most dangerous?  I have the means to protect both of us, but only for --" he hesitates, and then says roughly the equivalent of saying '23.98 hours', as if he's not used to the units he's trying to use.

(Questions! Merrin has them! So many! He has means to what– oh, actually, that would de-confuse her about his apparent immunity to both heatstroke and hypothermia, though at the expense of confusing her MUCH MORE on the nature of Reality.) 

She can give him a report. That's easy, and buys her time to find a way to ask about the food that doesn't feel as mortifying. 

"The cold hasn't been the hardest part so far. I arrived 21 planetary-days before the spring equinox - I don't have the data to conclusively calculate year length but I suspect it was late winter - and I was able to survive the first night with more minimal shelter than this. My sleeping bag is rated to -20° C and I had stored battery power to run the suit heating," gesture at the plugged-in power armor in the corner, "for the coldest part of the night. ...The heat is already a problem and will get worse. So far I was able to manage the afternoons staying in here with ventilation from deeper caves," another gesture at her setup, "and it was unpleasant but not life-threatening. But my climate model thinks the temperature will get up to at least 60° C, and when the nights get shorter it'll cool down even less, it's possible it won't drop below freezing, the only way the shelter warms up slowly enough is if it's below freezing at dawn. Options I'd been considering included finding a deeper cave system that'll stay cooler or building an indoor pool to sit in water during the day." 

Pause. "...Right now the dangerous heat period is much shorter than - your thing - would be. That could change." 

"Hm.  It's possible I get more ability to protect us at dawn, or alternatively, at 22.98 hours after the previous moment when I first woke up and was able to speak to you.  If you are confident in our ability to otherwise survive the entire day, even should my capabilities fail us, it is possible I should apply those capabilities at dawn or at the 22.98-hours-later moment as determined then, and gamble on the capabilities being renewable."

"I have another capability for repairing my protective suit, which I infer you to have cut off of my injured form.  That capability may or may not be renewable and might operate to repair your own equipment -- or other important broken things -- although I am not, actually, sure about that part.  Do you have priority repair tasks that should take precedence over my own suit?"

Iiiiiis Merrin going to ask any of her questions or is she just - freezing up - from the combination of suspicious-paranoia and feeling like when one is suspiciously-paranoid one should avoid blatantly revealing that fact??? 

That's stupid. 

Merrin is really really bad at social deception games, okay? And she is absolutely certain that she would never, ever beat Estha at a social deception game, which means that if she tries she's going to be weird and furtive about it. 

Better to pick a strategy she can actually execute. 

"I don't have any high-priority repair tasks," she says. "So far I've been able to maintain all my gear with the tools and replacement parts I had," albeit the replacement parts lately have all been coming from cannibalizing other equipment, which isn't sustainable. "...But, um, if you're modeling that I understand your repair capability or any of your other capabilities, I...think...the thing that happened edited that out of my memories, and I have no idea what the limitations are, or why your capabilities might be renewable or might not." 

"I was accepting responsibility for tracking that on my end, yes."  This culture wants him to be having facial expressions all the time -- well, actually around only a quarter as much as other Golarion cultures, but still a lot by Chelish standards.  And yes fine Esta will do that and just make sure he's doing it consciously.  "Assume a corresponding deficit on my own side with respect to your own equipment.  I now have no more idea of how you cut off my protective suit, or the purpose and operating principles of an electrocardiogram unit," as one of the readable labels said, "than, I expect, you have of how I produced the food on that table.  You should eat that, by the way, it's bland but fully nutritious and you have clearly not been eating enough, Merrin."

(And for a moment he is sounding, speaking, and behaving exactly like Estha.)

She really hasn't and she's so hungry. 

(Now that Esta has Cultural Adaptation it will be somewhat apparent that Merrin is unusually emotionally-expressive even relative to cultural expectations. She doesn't seem to be putting in any effort to moderate it, as though she's never been punished for anything in that class at all.) 

...Wow that moment was kind of uncanny. Merrin can handle "the vibes are off" but it's extremely jarring and disorienting to have the vibes sometimes off and sometimes so reassuringly right. 

Is it a good idea to eat the mysterious-capability-appeared food? Like, there's an argument that it's not as though it's a worse idea than eating alien snails but also WHAT IF SHE'S NOT BEING PARANOID ENOUGH but also it would be awkward to argue with him about it now and augh. 

"I knew way more than you about the medical equipment even before this," she says with a smile, "but I'll keep that in mind. ...Are you sure that whatever happened to me wouldn't have changed my biology such that food you - produced - is no longer safe for me to eat?" 

For example because he's a SHAPESHIFTING ALIEN, not that she really thinks that's likely, and if he were a shapeshifting alien then he clearly at least understands biochemistry enough to fake blood with all the right components to look normal on labs. 

"...no, and my failure for not thinking of that."  WHY did he say that, Mariona is not his superior -- this culture thinks very strongly that it is appropriate to say this even if, or especially if, Mariona / Merrin is his subordinate??

After another moment's thought, "I believe I have a capability that ought to prove fully able to rescue you if that is the case, however."  Heal works on aberrations.  Heal works on outsiders.  It would be truly odd for it not to work on 'Merrin'.  Unless she's running on Negative energies now??  But no, that would just be stupid.

“…Okay.” And Merrin does also have drugs to handle it if she has an anaphylactic reaction and it would be silly as narrative tropes go for her to die of this after all these months.

….She’ll have one mouthful of food and wait a while for any sign of a bad reaction - and explain her reasoning on that to Estha - even though (bland or not) the food is amaaaaaazing and she wants to eat FOUR of the breads-with-stuff-inside RIGHT NOW.

Ugh. She wants to ask him about the inexplicable intermittent Baseline-aphasia thing but it’s still weird and awkward to talk about it while maintaining paranoid suspicion and trying to do a social deception about that— that’s being silly.

“What’s your own understanding of the - language difficulty - you’ve been having intermittently with speaking Baseline?” she asks him, while trying not to stare too longingly at the breads.

"That your own understanding of language has been -- inverted -- and I'm using up capabilities to synchronize with the inversion.  Of course, it could also be my own understanding that's been inverted.  Your version of the language has many concepts of hidden order that are now missing from my own."

"In about two hours I'm going to stop being able to speak your version.  I can give you the ability to speak my version, and that would last a full 23.98 hours.  I've been hesitating to do it that way because I don't, actually, know what full effect it's going to have on you, if you can speak both."

...actually, what if he gave her Utopian(*) instead of Taldane, that's probably less something that might explode on contact with Baseline?

(*)  For some weird reason, a bunch of outsiders and even some Golarion polities, if they want to write a contract in a Lawful language at all, will insist on doing it in the language of Axis rather than the language of Hell.  Esta speaks Taldane, Infernal, Utopian, and Draconic.

Nod.

“Can you explain the mechanism of action for the capabilities you would be using on me? I think I’m having trouble reasoning about what might go wrong that’s prompting you to hesitate. …Are you noticing cognitive side effects on yourself, from whatever you’re using right now to understand me?”

Merrin CANNOT IMAGINE what hypothetical cognitohazardous memory-editing exposure could write the entirety of the Baseline language into her brain??? You would have to alter SO many memories??? …Reality doesn’t stop at the limits of Merrin’s imagination, so that’s not a conclusive argument, but it might be evidence.

"I definitely am getting side effects, yes."

"And... I am frankly not sure where to start explaining.  My memories think Merrin is supposed to know all about this and have her own set of capabilities to use, though mine are stronger.  Rather as I expect your memories say I am supposed to know all about, say, that protective suit there."

Esta gestures at the Exception Handling exosuit, which Estha would have never once worn or maintained in his entire life.

…Speaking of that, Merrin is getting pretty cold, wearing an emergency blanket that she grabbed is not cutting it, and she would normally just get into the armor once she was up for the day but she would rather snuggle Estha. Even if he might be an alien shapeshifter, apparently.

She gets back into the sleeping bag with him and snuggles up (though she's not herself naked, she's sleeping in her dath ilani underclothes-layer). 

There are 'capabilities' that one might say that every dath ilani has. Like basic math and basic everyone-learns-in-school engineering, how electricity and circuits work, that kind of thing. But...in her own memories, she and Estha were pretty differently specialized! ...Honestly, she doesn't even know that much about what Estha did with his time that was not dates with her. Something of significant value to Civilization, presumably, since he could afford a masochist girlfriend, but probably not Exception Handling and definitely not endurance field trainings.

...Her Estha could not have climbed a near-cliff like that on his first day on a new planet with lower oxygen. Perhaps she should have been paying significantly more attention to that. 

"In your memories, do we work for the same department with Governance?" she asks him. "How do you remember us meeting?" 

"Same department of -- not exactly Governance."  His Cultural Adaptation is not a match for whatever conceptual conflict he's running into.  "Your version of the language now completely lacks the entire set of concepts for what our -- department, did, exactly.  We... dealt with... entities, there's no longer a word for them, or what they do, or how to interact with them."

"We met during your earliest training.  I was one of your instructors."