Due to a series of events beginning with my ex contacting me, followed by me saying "negative" things to her, followed by her new bf emailing me and telling me how "deeply hurt" she was and to "not contact her anymore" and ending his email by saying "if you have anything to say feel free", he dangled a carrot in front of me that was something I had been dreaming about for months.
So stupid me said "as a matter of fact I do have something to say that could save your life if you promise to keep it confidential." He agreed and I proceeded to send him an extensive email documenting my relationship with her and ultimately telling him about BPD and if he chooses to stay with her that he needs to understand fully what he is dealing with. I even sent him links to this website saying I wish I had had these tools.
True to form (just as I did to others in the past) he tore me a new butthole defending her up and down. Saying things I myself had once said. "This will draw us closer together." "I will help her because I LOVE HER." on and on. He used the "people have noted what a positive influence I am on her and how happy she is!" He was ME in EVERY WAY.
It was really dumb of me but honestly part of me is glad I did because someone way back when warned me explicitly and I said the same things. To this day I wish I had listened to that person. Maybe someday he too will look back and say "I was warned." So I apologized for saying what I said and that was that.
I would not recommend this course of action to anyone as it cause a host of other issues but the door was left open so I walked on through! Oh well lesson learned.

It was somewhat liberating knowing that nothing has changed with her and cycle is just continuing business as usual.