Nobody was ever supposed to die.
In this particular case, she did the fault analysis half-subconsciously in about thirty seconds, and - well, it doesn't mean much, that she can't see any obvious mistakes. The majority of Civilization is smarter than her, anyone involved in Governance is a lot smarter than her, and anyone making decisions on the scale of 'should planes be stocked with parachutes' is going to spend four orders of magnitude more time on this particular no-longer-hypothetical scenario than she has, right now, and so it would be actively surprising for there to be errors in judgement that she could perceive.
This may or may not be a rationalization, but it helps, and Merrin is super not inclined to spend what are probably the last few minutes of her life poking at whether her emotions are a proportionate and calibrated response to the situation. If she wakes up later - and she's not going to, clinging to that hope is a level of rationalization she won't tolerate in herself - but if she did, that would be the time to process a thousand feelings that don't, in fact, matter right now.
She takes all the right actions. Probably. Merrin maintains certifications for half of Exception Handling. She's aware that you don't get to know, in real emergencies, or even in re-enactments since it would sort of defeat the point if they weren't realistic in that way - and this time there won't be a debriefing and analysis, afterward. Which is mildly frustrating, if she's going to die in a freak plane crash she would at least like credit for being the person to stay calm and orient quickly and help the probably-terrified airline staff to coordinate who exactly should be doing what. She can– no, she's not going to bother keeping a mental list of petty frustrations to debug later in her personal analysis, what would be the point, and she needs all of her working memory right now.
For such a small number of minutes, there are really a lot of petty emotions that she has to consciously remind herself not to make memory handles for. Her parents are going to be traumatized, and – wow, okay, apparently the way she feels about that is 'I wish they wouldn't do that', which is obviously incoherent because it's not like she wants her parents to love her any less. It's hard not to feel guilty about the fact that flying around the world as often as she does made the probability of ending up in the one freak plane crash a lot higher, even though she doesn't regret anything, and - well, even if she had been optimizing for a safe life over her best life, why would you avoid flights, planes just aren't actually very dangerous. Except for this ONE TIME, APPARENTLY and it would have been MORE POLITE of reality to pull this on her return flight, she's had an incredibly busy month and she really needed her upcoming date with a particular millionaire possessed of infohazardous tastes in bed.
She's going to miss this year's Alien Invasion Rehearsal and she's annoyed about that, she was looking forward to it and she spent a lot of time preparing, and it's stupid to now feel like that time was wasted, it wasn't. Even in a horrifyingly broken version of Civilization - which is the sort of hypothetical you spend a lot more time contemplating when you're an endurance EMT who also keeps active Exceptional Circumstances Certifications with five different organizations - but even in a world where bridges collapsed and planes crashed and wildfires destroyed towns, even in a world where True Death could come to you with a heart attack or an infection, you wouldn't just...spend your life refusing to ever plan ahead.
There's a four-year-old on the plane. This is also VERY RUDE on reality's part. They're trying to improvise a parachute - or, well, Merrin isn't actually working directly on that, she's not an engineer, she was coordinating the team at first but someone else on the plane turned out to be an infrastructure project manager and he's not as practiced at Merrin at quick-and-dirty-satisficing but it's still a better fit. She's not comforting the kid because the kid's mother is there and that clearly leaves Merrin with no comparative advantage for it. It's still really distracting.
...She's a little wistful that she never figured out the sex thing. It's not like it was ruining her life or even especially making her sad, she's never been an Ace Girl Who Feels Like Being Ace Is An Angsty Curse And Knows Society Thinks She Doesn't Need To Feel That Way But Fuck Society Actually*, she was pretty content with her cuddlefriendships, she didn't have time for more commitment and of course sex isn't the same thing as commitment but it sure does appear to correlate. And then the Keeper approached her, and that was just a bonus, discovering that the dark joy and satisfaction she's always found in pushing herself to her limits - in hiking twenty miles over the course of twelve hours with all her medical equipment on her back, in staying awake for thirty hours straight, in running and swimming and climbing until her muscles burned and everything felt sharper and clearer and brighter - did, in fact, correlate with liking certain other things, and allowed for some very mutually beneficial exchanges with excitingly attractive millionaires possessed of complementary tastes. (It's mildly inconvenient that this is considered an infohazard. It would be different, if half of people were like her. Of course, Merrin's entire life would be very, very different if half of people were like her.)
In any case, though, she had intended to get around to chasing down those trailing threads of her sexuality eventually, to nab even more of that delicious bonus utility, and...in hindsight, pushing it off to later probably was just a rationalization. A symptom of the fact that, whatever one can say about her talents and hard-earned useful skills, however much evidence she has to point to of her conscientiousness and determination, she's in a certain sense lazy. Low curiosity, the career advisor said, and - it's odd, in a way, to look at a life half spent training the skills to handle dozens of out-of-context disasters for Civilization, and say 'that person likes to stick to their comforting routine', but it's sort of true -
*A four-syllable word and common Gendertrope in Baseline.