Oh, mom2BPD... .
I know how you feel... . When it first happened to us, we were devastated. Especially since there were also 3 grandchildren involved, who we were close to as well.
There is no easy fix for the pain. There is hope though - every person w/BPD is unique and also their personal situations. It has been my experience that especially girls tend to renew contact.
My therapist says to put invitations out to her with no expectations and see what happens and leave little things at their door that she and gd like. So that's what I'm doing for now.
What is your experience with this?
I think this is the best advice you could have gotten. Keeping that door lovingly open, and keeping a discrete distance so she doesn't feel smothered by your attempts. You know your girl the best, and so will be able to determine how much is too much and how little is too little.
In the meantime - it's best to focus on other things as much as you can. At times that you need to focus on your girl, try to educate yourself on BPD and the effective communication tools, so that the next time you can skillfully navigate the mine-fields of BPD... .