My ex had a knack for twisting everything into being my fault. It basically happened every time we fought.

One that comes to mind is I told her that I didn't want to watch the last episode of our favorite show (Finishing a long series always makes me feel depressed for some reason). I told her repeatedly and in no uncertain terms. Well she decided to put it on and have us watch it anyway because she really wanted us to finish it.

When I figured out she intentionally crossed a boundary, I was really upset. She apologized and in the following conversation, I forgave her and made a comment about improving/being more mindful/trying not to do it again.

That made her flip shit! Apparently saying something like that was cold and unempathetic. It really hurt her when I act that way. More than that, I was deflecting blame totally onto her! Why didn't I do more to prevent it? All of our fights seem to always be her fault! (Her crossing my boundaries was pretty common). Certainly it can't all be her fault! Relationship problems are both people's responsibility. Why can't I ever take responsibility for any of my actions?! She accused me of being the emotionally abusive one.

It sounds so stupid typing it out but that kind of stuff worked really well on me. At the end of it, I apologized for being a shitty girlfriend and was convinced that it was all my fault.

The weird thing is after a while, I'd come into these interactions prepared. I'd discuss some of our issues with my roommate and get her take. Roommates logic was crystal clear and felt objectively correct. Didn't matter. All of that evaporated and her abusive tactics would still work.

Truth be told, I'm still only 90% sure she was the abusive one with BPD and not me.