JPC, I've learned the hard way on more than one occasion that I cannot control others. I can, however, take care of myself and do my best to be supportive without being codependent. I can also try to set a positive example.
With BPD her moods can shift in a very short amount of time, so she may go from being distant to wanting to communicate. It's hard to say. You do have some power over how you interact with her.
The Lessons to the right of these posts contain some good information on taking care of yourself and learning to communicate with your loved one. A good communication technique is called S.E.T. Have you tried it?
https://bpdfamily.com/content/ending-conflictHang in there!