
I'm sorry that you're having to go through all of that. It can definitely be hard, and the lack of physical affection just adds to the strain. I think that many of us here can relate to that.
I'm a bit confused by your question at the end. Are you asking how/when a person knows that it's time to walk away from the relationship?
That is dependent on the individual and their circumstances. We each have our own level of tolerance, inner strength, and priorities. A relationship that works for one person does not necessarily work for another. No one can, nor should they, tell another when enough is enough in a relationship.
As for her not wanting to talk to you about things, it may be very hard for her to do. People who present BPD traits tend to have an intense shame response. There are communication strategies that can be helpful in getting others to be more open and communicative about what they are experiencing inside. Listening with empathy and not invalidating the other person can go a long way at making that happen.
You mentioned seeking outside help with the relationship. Did you ever work on communication skills in those sessions?