Hi, I'm not from LA and I don't know about any good places near you to seek help. However, I wanted to welcome you to this group and let you know that you are in the right place. Reading through the information that the group members have provided is really helpful and I have gained insight into my own life by reading what other people have written about theirs. You are not alone in this journey.
I hope that a group member can help you find something local. If not, here's a link to the National Alliance on Mental Health
https://nami.org/Home. This website can help you find local resources. That being said, I'm really sorry that you and your loved ones are going through this difficult time. You are really wise to seek out help to prepare yourself and to learn how best to support your daughter when she reappears in your life. If you haven't read it yet, you might want to read Stop Walking on Eggshells by Paul Mason and Randi Kreger. The book helps families of people with BPD to understand the disorder and how to support their loved one.
My daughter is college-aged, too. It's tough watching her struggle with BPD. Sometimes, it's also tough being with her because of her behavior. I know that she's in pain and I often feel torn between being there for her and protecting myself. The people in this group are really helpful in helping me to understand what's going on and how to both be supportive of my daughter and protect myself. I hope that this group can help you find some peace, too.