generally speaking, people with BPD traits are highly impulsive, and reactive - reactive to pain. they have poor coping mechanisms, and poor relationship skills.
i dont think thats to say someone with BPD traits cant be highly manipulative, or cant think anything through.
it is to say they arent devious relationship geniuses that set out to hurt us. when a relationship is breaking down though, there can be a lot of self preservation on both sides, and that can certainly be hurtful.
lets walk through a few of your examples...
Triangulation - both to create jealously or show how desired she is, as well as to create competition for her.
this might be better understood as "jealousy induction" than "triangulation". a drama triangle is something everyone is engaging in, and it has a payoff, not something someone does to us. dropping little or big things to make a partner jealous is something that ive done myself; lots of us have, in small ways, and it comes from a place of insecurity. people with BPD traits are, inherently, insecure. im speculating, but this probably did not involve a deep thought process on her end. its probably just something she knows, that has worked for her before, a way of getting your attention, and a dysfunctional way of getting needs met.
Gaslighting - telling me I'm jealous and controlling for not trusting her when she's getting text from dudes to hook up. Projection - telling me i'm manipulating her and I have anger issues.
you would need to be more specific here. people that cheat can certainly be defensive and secretive about it.
Push / pull cycle - breaking up and getting back to together. Idealize and devalue
this ones on us. it takes two people to get back together. there are reasons that either party might do this, like difficulty being alone, or perhaps the breakup wasnt sincere but instead a means to get ones way/make someone change, or in general, not being done with the relationship...too good to leave, too bad to stay.
Mirroring - She would say "we have so much in common it's like I'm dating myself."
couples say these things, especially in the beginning stages of a relationship. mirroring is something that we all do; it facilitates bonding. people with BPD traits just take it to extremes.
Constant comparisons to her ex
this could be jealousy induction or unfinished business with her ex.
When we would fight she would constantly say "listen to your tone.. this is what I'm talking about"... totally makes someone feel crazy...
i know exactly what you mean here. people with BPD traits can be highly sensitive to tone, body language, facial expressions, etc. at the same time, if you were fighting, you might have sounded a bit exasperated .