It might help to research BPD online and see what you think and how it fits your daughter. Maybe to become aware of behaviors and what issues they deal with. It is difficult to deal with someone who is angry all the time. Our ES is also angry all the time, and he usually makes something up just to hit us with. HIs personality disorder is something different. We have learned through counseling and various books how to recognize his manipulations and thinking patterns. This is not the cure or fix but it helps us cope and move on and not get caught up in trying to fix him or cure him or even try to rationalize his attitudes with him. That is no win. We parents are on a bumpy ride and I wish you the best. I found we had to look at this as a death of a dream for our ES to be healthy, happy, and functional. Its more than his verbal abuse and anger, its knowing his life is chaotic and angry and he is satisfied being that way. Something we would not choose for him, as you said.

I feel for you my son is disabled and at times towards the end of our time as a family I felt like I was in an abusive relationship. It's so hard when it's your baby too. It's not something they teach you in parenting classes. All I can offer is you need to love yourself I won't suggest you walk away I know it's not that easy. But try to do something good for yourself each day even if it's only a walk in the sunshine. It's the little things that help.