Justifying their behavior by saying it's PMS/their period

I honestly can't stand that my pwBPD does this. She uses it as a catch all excuse to justify her warpath against me almost every month. The hilarious part is she has an IUD, so there's no overt signs it's her period or she's PMSing like most women. So half the months she claims she's being terrible to me it's not even the same time of month as other months she uses the excuse. Then she admits she's not entirely sure if she's on her period or not because there's no actual signs. So really, you're just being a horrible person to me because you want to be.

Anyone else have this happen?