We've been there with my step-daughter talking about not wanting to live - it's such a scary place to be - especially when they are adults and live on their own... .
You can only be there for her to the extent that she allows you to be, which is scary AND frustrating.
I guess that I'll just continue to talk and learn what I can about BPD but getting her back into therapy is my first priority.

Being that safe and consistent person in your daughter's life is priceless - there is lots of information here (including articles, workshops and book recommendations).
There are two very good videos by Xavier Amador (a clinical psychologist) about getting our loved ones into therapy:
https://www.youtube.com/watch?v=Lstn6WNnCRc&list=PL72EA4FADA3E36ECFhttps://www.youtube.com/watch?v=VxiBgq5G-cI&index=2&list=PL72EA4FADA3E36ECFEach is 50+mins, but worth watching. He talks about Schizophrenia, but the same principles apply with getting our loved ones w/BPD into therapy.
There is also an article on the same topic which you may have already read:
https://bpdfamily.com/content/how-to-get-borderline-into-therapy