Before I ever started dealing with these issues with my d16, I'd heard the stories about my h and his ex- my first exposure to this illness. If my h wasn't such a generally honest and non-dramatic guy, and I hadn't seen some of the exes emails (and later been on the receiving end of her drama) myself, I might have thought my h was being a stereotypical guy with the old "my ex is crazy" line.
My h went to counseling for years on his own, to deal with her stuff. They tried couples therapy, but she would fire the counselor if there was any hint that any of their problems were hers. It would go like this: They talk for an hour about h's problems and strategies for him to be a better husband. If none of her stuff came up, she would say "There must be things about me you want to change, why don't you ever talk about those, don't you care?" If the T made any suggestions for that she might want to look t her own behaviors, she was out of there, the T was terrible and incompetent.
I liked my d's counselor, she wasn't terrible, and she probably helped keep my d from suicide at some points. On the other hand, my d did have her totally snowed about a lot of things, they kept deciding together that she didn't need counseling, that she would be "on call" because my d was doing so well. No matter how many times I'd say, look, she needs skills she can only work on when she's not in crisis, so she can learn how to deal with the NEXT crisis. Because there WILL be one. But... .nope.
Long way of trying to be supportive and say that you should trust yourself. BPD means having an unstable sense of self and a strong urge to protect from perceived threats of rejection or abandonment. Makes them REALLY good at creating a make-believe reality for others.
My d... .I'm shaking my head right now. She can look SOO normal. And then she can fall apart so drastically, all in the space of hours. Or minutes.
No matter how much I want to trust the "she looks ok now"... .it doesn't last. Or, it hasn't yet. Maybe someday. Trust your gut!