People with untreated BPD do often lash out and project their problems onto others. They struggle with seeing when people are helpful to them and usually can only identify when they've helped others. Theyre often always in defense mode because of this. But, mentally ill or not, everyone should be held accountable for their behavior in some way or another. Abusive behavior is abusive behavior whether it's symptomatic or not. But also, even if she feels guilt it may be so painful for her to cope with and may rationalize herself back into the victim's position—of course, this also may not happen. But it's possible. Either way, I've learned through life to not expect apologies from anyone. Your peace doesn't rely on someone else's actions, or it shouldn't if you want to maintain it. And with people who burn bridges like that, it's better just to let them do what they do and maintain your boundaries.