She’s going to therapy but this type of thing probally takes a long time to diagnose and fix.
That sounds like a good sign. Yes ... it will take a long time to diagnose and to help her cope, heal and live with the condition. Think diabetes. That would never go away really, would it. But if someone tends to it, you can live a great life with diabetes.
This is not a whole lot different.
And do not underestimate how important your role can be. There are lots of good resources regarding how to live with someone with BPD. Provided the relationship is not abusive, provided your partner is willing to put the effort in to be honest and transparent, then it sounds like it would be worth it to spend the time and effort on your end to get to the bottom of this relationship - you should get counselling for yourself too.
Rev.