Turns out that my cousin is TWAW. She messaged me after I posted something on Instagram 'wanting to clarify what I meant'. Short conversation later I clarified that I believe sex is binary and immutable and she clarified that she does not agree.
No one was nasty or anything, although I think I could feel judgement her end.
I feel sad that she likely thinks I'm just a bigot because of course an Instagram post and a short text conversation does not illustrate my point in any sort of detail.
This is something I've given thought to every single day for over 4 years, it's not a knee jerk bigoted reaction.
I don't have much to do with her anymore although we did used to be close.
I just feel sad I suppose.