i just think. that there is an elevation to arthur dent's character (specifically her ultra turbo repression) that cld be explored through her gender, and the realization that her gender is not the one that she very much insisted it be (as enforced by the social expectations she grew up in)
like the whole thing of arthur dent being the very best of polite british society to the point that she's funny for how much she adheres to it, especially once the earth Bload Up, and how she's trying very hard to hold onto those conventions as a sort of preservation of the earth. bc part of her whole thing is that i don't think she was particularly happy on the earth either, but it's the benefit of hindsight once its gone, right? she's going to find things to miss, because that was her whole life. there's a sort of freedom that comes with that, once she's not constantly running for her life and finding the next spot she's going to fall asleep in.
i think she would be adverse to changing at all. which is why it's so interesting to think about what if there was a situation in which she was forced to confront the ever-present It that has been floating above her head since she was a child. the What If. the thought experiment that she had to bury because it wasn't the "right" thing to be, because she won't be taken seriously if she does indulge in It in any way.
arthur's already not taken seriously in the heart of gold era. she's belittled and left out of explanations, treated as lesser than by zaphod, and doesn't know what's going on unless someone thinks to explain it to her. and the abandonment of earth conventions (from social contexts to the concept of the calendar) i think really gets to her. i think it makes her skin itch with the loss of her entire planet. its not that trillian doesnt care so much as she was jaded by those conventions, and didnt particularly like subscribing them in the first place. like she left earth. tricia hates the slog. but arthur sort of liked it? she liked how mundane it was, the lack of the constant threat of danger (which, funnily enough, is part of why the thought of indulging in any of her gender was dismissed outright. it was too dangerous)
so i dont think she would transition normally, no. i don't think she would have a big revelation and go hi guys i am and always have been a woman, as much as i think that would be sweet in a different story and a different context. i think the revelation has to be plucked out of her like a beautiful shining star and shown to her, and she would clutch at it protectively because that's Private, that's Her, no one is meant to see that because it was never supposed to be her in the first place. protect her from even knowing things she does not know she doesnt know.
but i think the heart of gold crew wouldnt blink twice. i think theyd be accepting in a way thats borderline underwhelming. there are like a million species with a million different gender presentations, and her brain has to hold onto the convention that its not okay because then if she doesnt she has to admit it wasnt real in the first place. and i think part of her would grieve that in the same way that shes grieving the earth, because those two things are sort of one in the same.
there'd be a whole slew of emotions. embarrassment, at being seen. anger that they're not mad at her, but then anger at the fact she could've had this. anger at the fact she wouldn't be able to see what earth thought of her. angry that she's changed.
i think trillian is a huge balm, because she's the only one who understands why arthur's reacting so severely. i think they're able to get closer because of this. i think all of them do, to be honest? because arthur is so bundled up in those layers of repression and politeness and making herself small so she doesn't get killed, i think that this is the most genuine thing they've seen from arthur so far (aside from ford. he's seen glimmers of her beneath the surface). being seen like that terrifies her. but they like it? and that terrifies her too
and ftr i don't think she's a binary trans woman at all. but i do think there's an initial misunderstanding (by her) that she must be. but i think she'd eventually figure it out. she'd get more comfortable. like when she was the sandwich maker.... ahg.
anyways. i've rambled enuf. i pass on my baton. think about her with me, ok? take my hand