I tried talking to her about tolerance, shame, and sexism, but it she is dismissive of all of it.

Did you also try listening to her about how much it sucks to be bullied? Or how much it sucks that you and her father didn't adequately prepare her for the reality of Auntie's porn career, and how you're sorry you made that mistake?

Your whole post is about a young woman who literally has no safe place of her own -- her parents lied by omission and her aunt is not who she thought she was. And when that led to school bullying, you talked about "tolerance, shame and sexism." So the girl is hearing from ALL SIDES that she is the problem. And she's fourteen, struggling with bullying and with learning that her family keeps things from her.

Does it suck that she said things to her aunt? Yes. But it has also sucked to be her, because of the adults who made choices without her knowledge and consent that affect her anyway.

YTA.