Once I left the bar, I told her, “fuuuck, it’s like I’m the only sex-repulsed person in the bar, and no one respects it in there, but thanks for being someone I can confide to out here.” Her flirtiness dried up almost immediately, and she insisted that she wasn’t flirting with me for the couple hours prior, like she was trying to edit the past.

It sounds like she was following your lead. You pretended out of politeness that she hadn't been the one flirting with you, so she thought she was being polite by doing the same. Or she was embarassed.

Lots of people are oblivious and don't realize when someone's flirting, so she might have assumed that's why you weren't reciprocating. There's no way she could have known you were repulsed by sex until you told her, and when you did she stopped flirting. I get that you're bothered by people flirting with you, but there isn't anything weird or rude about her behavior. Just a bit of unavoidable awkwardness that comes with socializing.