Alfirin isn't entirely sure she doesn't want to take Lilia as an apprentice. The initial meeting wasn't an assassination attempt (She checked beforehand, of course) but that doesn't mean it's not part of some larger ploy beyond her limited ability to foresee - 

- if Lilia was being truthful, she wasn't being honest. She gave only cursory reasons for choosing to apprentice under Alfirin and for avoiding Arazni; If those had been the sum of her reasons she would have picked any other eighth-circle and not requested secrecy in her introduction... Probably Lilia has more reasons to avoid Arazni's attention, and chose Alfirin as the wizard most likely to go along with the request for secrecy. Alfirin has never been to Arcadia, maybe the court in Xopatl really is a place where you can get to fifth circle. Or perhaps she's Azlanti and avoiding close acquaintances of Aroden's - either way it leaves the question of why she's here with the crusade in the first place. Most fifth-circle living wizards of Lilia's apparent age aren't selfishly worried about Tar-Baphon's eventual victory in twenty years, if it comes at all. Altruism would be an unsurprising motive but for some reason Lilia didn't mention it - if she's being literally truthful the reason might be that it doesn't move her at all. Interesting.

What if she wasn't being truthful? If it's all a lie - then Alfirin knows nothing, except that someone has gone to the effort to weave a very confusing deception to no clear end. For the sake of being mysterious, to be bait in a trap, perhaps, but the trap would have to be one that works even when the bait is recognized as such - 

"Curiosity, remind me tomorrow to research demon lords, I vaguely recall there's one obsessed with puzzles..."

- Is there anyone else who'd set a trap like this? Tar-Baphon probably not, at least not for her, it might be a play at Arazni - it could be one of those hags from Brevoy, if they weren't all dead - she should confirm that they're all dead - nobody else comes to mind who'd mix this degree of convolution with this degree of unsubtlety. (It's pretty out of character for Tar-Baphon too...)

...And the third possibility, what if Lilia was being mostly but not perfectly truthful? If there was one lie, or two - Where she is from and/or whether her enemies can follow her, Alfirin thinks.  The first world, or the city of brass, or Hell. Most likely the first world, though in that case probably there were no lies after all and it was all technical truths...

The next day, Alfirin goes and finds Marit.

"I would like to give you certain information, conditional on your agreement not to use that information outside of particular circumstances."

"I so agree, though I may or may not use it under those circumstances. What?"

Glitterdust.

She hands him a fat sealed envelope. "Contents to be read with my future permission, in the event of my suspicious death," which of course just means 'death', "disappearance, apparent enchantment, or other circumstance of that kind which you think I would have listed if I'd foreseen it and taken an hour to list every possibility. The password is 'jackalope'. You may do whatever seems wise with it in the meantime, so long as that is consonant with keeping the contents and their relation to me secret... don't give it to Arazni. You may have someone who doesn't speak Kelish copy it. If I ask for it back and you have no other reason to believe I am enchanted, I would like all copies given to me one month later."

"All right." He takes it, and slips it into one of his bags. Squints at her, though it would only be slightly useful in determining whether she is already enchanted and acting oddly. "Anything else?"

"That was it. Thank you."

He has it copied, by someone who does not speak Kelish and lives several hundred miles from the front lines; he puts one copy in a hole in the ground in the middle of nowhere in particular and keeps the other on his person. And he watches her. 

(Not because of this. She's among the people he just watches closely anyway.)

"I have decided I will teach you. What can you do?"

She's leaning yes, to the only important question, but she is not yet committed on it. "A great many things but most of them enchantments, and so less applicable here." She has considered what can be shown off without suggesting that she is a time-traveller. That she can touch a magic object and make it appear nonmagical without casting a spell, sure; that she knows an astonishing variety of torture spells, probably not. That she can speak to a sleeping person in the same room and learn their secrets without their recalling it, happily; that she can do it from across the continent, no. 

She can also do all of the sensible things there's no excuse for a fifth circle wizard to be unable to do, like Teleport, or Dimension Door without moving or speaking, or turn into an invisible cloud of gas. She knows her magic silently and without motion but not at range; it is very nearly impossible to startle or frighten her, but she in fact has no experience on a battlefield and this is very readily apparent. Her instinct in a fight is to flee it.

Alfirin brings in a cleric of Abadar unannounced on the third day, so Lilia can tell her under a truth spell that she hasn’t lied to her. She’s not surprised when Lilia can, and doesn’t seem to take it as very much evidence about Lilia’s honesty, but of course one way to beat a truth spell is to have everyone convinced that you can beat a truth spell and there’s no point bothering; it would be foolish not to at least check. She warns Lilia that someone will probably try looking into her past, once they notice that Alfirin has an apprentice who’s lasted a week. 

She's sure.

She was sure right away, really, but held back her judgment for fear of being sentimental. 

If she were wrong she’d be betraying her mother’s secret to a powerful wizard so she waits to make sure she’s really, truly sure.

But Lilia spent decades as her mother’s student. There are differences, of course, but they’re the differences you’d expect from someone pretending to be an Asmodean Chelish archmage compared to someone pretending to be an idealistic crusader. 

There aren’t two people like her mother. If there were, the world would look very different. 

At some point the risks of waiting for more certainty are higher than any conceivable benefits. They'll look into her, and she should fear that this will somehow turn up that she’s sold her soul, though she’s in fact not sure if she has sold her soul or not, in this timeline. She still has her arcane sight. Everyone’s been assuming it glued on by magic. She’s not sure if devils can reclaim their gifts if you go off and time travel with them.

…reason to tell Myrabelle-Alfirin sooner, so Alfirin can figure out if Lilia is worth protecting and if so how to protect her. 

"I'd like to explain my secret reason for wanting to work with you. Is there a good place for us to speak privately?”

"How much privacy do you need?"

“It is important to me" to you, therefore to me, "that Arazni could not overhear us if she wanted to.”

“That’s a high bar. I do not believe her to be able to listen in on a telepathic conversation inside a private sanctum inside a full rope trick.” But of course she can offer no guarantee.

“Let’s do that, then.”

Alfirin casts the spells and readies a dispel, then waves Lilia into the rope trick.

What's so secret, then?

I am from either a different Golarion or this one, nine hundred years in the future. In my memories, with which my possessions are consistent, I was the spymaster of Cheliax, which declared independence from Taldor in 4081. Aroden failed to return when prophesied. He’s dead. Arazni died in the Shining Crusade and was raised by Geb to rule his country for him in retaliation for Lastwall annoying him. Cheliax’s monarch came to power through an infernal pact with Asmodeus, and the country serves Hell. I don’t know which of these things your divinations might reveal, but - several of them might alarm your allies, obviously.

Yes, some of those are very alarming claims. That she doesn't particularly believe, not until she's figured out a way to check them. I could ask a number of questions but perhaps the most important is why you are telling me all this?

My mother was a Lawful Evil archmage. Myrabelle, in that lifetime, but I know she'd lived many prior ones. She wanted an agent in Cheliax, and I joined their government on her orders. When I arrived here the first thing I did - once I had determined that I had not been followed and would not be retrieved, and where I was - was look for her. 

I didn't have a list of previous lives, so it took me a little while to be sure. But I am sure now. You are her, and so I am at your disposal. She knows her mother, so she knows that the thing her mother will do about this is curse her insensible and Dominate her to learn everything she wants to know without an intervening person with an agenda. She knows too that it might be she is a liability in this lifetime and will be destroyed once her mother has learned all she can. She would be less useful, if either of those things mattered to her, so they don't. 

That is... less unbelievable than some of the other claims, and somehow more upsetting. All of it is horrifically, deeply upsetting to imagine might be true but this is - personal. Almost accusatory apart from how 'Lilia' gives no indication of objecting to her treatment at all. (Well, she is very good at hiding things.)

Suppose it's false. Why? To make her doubt herself? Probably not worth the investment if it's a high-investment scheme... what she's already seen is enough to qualify it as a high-investment scheme. The doubts this would inspire would not particularly help the Crusade's enemies, nor can she think of any personal enemies with the capability, inclination, and motive... It could be intended to reach ears other than her own and cause a breach between her and the Crusade. Still probably not worth it, but getting closer - worth it if there is in fact a plan Tar-Baphon expects to remove Arazni from the field soon, except insofar as this plot reveals that plan, unless he predicts her response to that would be to retreat to Heaven which is just as good from his perspective -

...Suppose it's true. The answers to 'Why?' are obvious enough; 'How?' and 'What to do about it?' less so. Lilia might know how, speculate on that later. What to do? Warn Arazni, first. Then... she doesn't know what, then. She has plenty of time to figure out what then.

First, to check whether it's true or false. If it's false and the most likely plot - she probably won't be able to tell on her own. It's worth checking with a dominate, but hearing under compelled honesty that Lilia's telling the truth won't actually be enough to be sure Lilia's telling the truth - she is not confident in her own ability to identify and unravel every possible means of deception, but she can question Lilia now and consult with Arazni after - 

- unless she can't - 

Don't resist. Greater dispel magic. Dominate person. Stay here.

She flies out of the rope trick, through the door, and shoves a set of spectacles into the hands of one of the surprised sentries outside the door. "Pink lenses, anything that leaves the rope trick is a lich." Phantom Steed, Haste. And then, after a few breathless moments careening through the halls of Overwatch,

"I need to speak with Arazni. Now."

They'll check it's her and let her through.

"Alfirin." She is, separate from the person at the door, determining it's really her, but more subtly; she'll gesture everyone else out of the room.