AITA for asking my ex with BPD to repay money she owes me?

I (M25) dated a girl (F23) for 6 months. I cared about her a lot, but her BPD and mental health issues made things tough. I tried to make it work, but it was draining my health, so I ended it.

During our relationship, I lent her $800, which she agreed to pay back. After the breakup, I asked for it, and she flipped out, saying I gave her the money to "seduce" her and that she "rejected" me (even though I broke up with her). She also said mean stuff, like she was never into me and was just bored. I think her BPD is messing with her view of things.

I just want my money back, but she’s blocked me. Should I keep trying or let it go? AITA?

TL;DR: Ex with BPD owes me $800, won’t pay after I ended things, and says I’m the bad guy. Should I pursue it?