I'm only skimming, but regarding Claire's friendships and stuff being realistic or no- as far as I remember just Marten and Emily know? So if other characters are shitty (although they're a liberal gang, and I hope not because if it wasn't the springboard for character development and maybe even if it was, that would make me hate someone), they haven't had the opportunity to act on it yet. Also, I mean, Claire probably felt with both Emily and Marten, before she came out, that they would be okay. It's not like she came out randomly to people she didn't know (like Becky in DoA, although of course that's different)- there hasn't been a lot of space for people to reject her based on her trans-ness. And Marten has known Claire was trans for quite a while now, and had an idea what she had done to transition (she said at the lakehouse that she had HRT starting a couple years ago. Also, Marten has a better idea than us, probably, of what a level of transitioning would mean in fiction Northhampton).
So, anyway, that all in account, I don't really see how likely it would be for Marten to reject her. There is some amount- he could discover that, in fact, he wasn't sexually attracted to her, but he's Marten, so he wouldn't be a huge douche about it even if he fumbled. I don't really see how anyone else would reject her, because there's just Emily, and Emily is a fairy who is nice to everyone.