Maybe you could first start with a family doctor by getting her physically evaluated--and see if that person has any suggestions. The problem, I see, is getting her to admit she needs help--and without that, you're sunk. Unless you can present evidence that she's a danger to herself or to others--then she could be placed in a mental ward and evaluated.

Would she agree to any type of counseling, do you think? Is she still with her partner or a partner--and if so, would they agree to relationship counseling?

Sigh. I had BPD and was actually cured. But I knew I needed help and did DBT * and regular therapy.

* Dialectical Behavioral Therapy

Meanwhile, there are books available to people to help them deal with BPD relatives and friends. One that comes to mind is Stop Walking on Eggshells.

Let us know what happens, please!

Note" Of course, we won't know for sure that she has BPD until she's professionally evaluated. But it sounds like you've done your homework on her symptoms.