If you got drunk, ran a red light, hit a school bus and the burned out carcass of your car landed in a no parking zone would you describe this event as a parking violation?
Technically, parking violation might be part of it, but to describe the above in those terms doesn't provide clarity to the reader - it miscommunicates.
I would describe your first incident as inappropriate contact with the ex boyfriend. Was triangulation
part of that - maybe, maybe not. She may have just been flirting and reconnecting and signaling her possible availability.
I get it. Call a spade a spade.
She was still madly in love with the first bf who cheated on, briefly recycled, and then left her, devastated. She was very honest with me about it in the beginning, which is why I took some responsibility for getting involved (though it was hard for me to deflect the BPD-like love attachment and desperation to have me around, even as a friend at first). Not until 2011 (Year 3), and the first kid, did I feel her completely detach from the Love of Her Life. I even found something she wrote to herself about it on our computer (with super idealization of me, joy at our family... the replacements for her emptiness). Up to that point, she may have tried to get back with him if he had tried. I helped her move beyond him, in a way (and no, that wasn't my purpose, it drove me nuts from the beginning).