Hi thinker,
I can imagine you are worried about your daughter. It's hard to look on when those we love, especially our children, are suffering.
Have you thought of showing your daughter this site or some of the information on it? Reading around the Boards and the Resource Materials is possible without actually joining, if your daughter isn't ready to take that step yet. You can recommend this link:
https://bpdfamily.com/content/what-borderline-personality-disorderOften reading other member stories can be even more helpful than general lists of symptoms and so on. That's where a lot of people have moments of "oh wow, me too!" that can be quite enlightening and helpful. So perhaps encourage her to have a look around the site and especially the Discussion Boards and see if anything resonates for her.
Do you think that might be a good way to start things off?