Wise, my daughter was a dancer also, and it breaks my heart that she let that go - it gave her so much joy.
You're right about the "fear of perceived and real abandonment." I have spent years in therapy, read the books on borderline, and still attend 12 step (Codependents Anonymous). I am not perfect, but I have worked very hard to use the skills I learned and to not abandon her.
Unfortunately and ultimately she has gotten worse because of the trauma she has allowed herself to be exposed to. She is the one who has cut off our relationship (and with most of our family also). I have no control over that. Having PTSD myself, I must confess that there is some relief in not subjecting myself to her unpredictable and constant rage of which I was her most frequent target. At 66 the stress and verbal attacks took a toll on my health. I have three adult children. The father of my oldest two was an addict, and years ago I came to the acceptance that my daughter and/or my oldest son, who is an addict might die. My suffering will not alleviate hers, so I choose to work on healing myself. Maybe that sounds selfish or callous. I live with both grief, some serenity, and even moments of joy in my life now.
I pray everyday for my daughter and all of us, and I work my side of the street with the tools I mentioned above.
I am my daughter's mother, but I am not her savior. I believe in a higher power, and I pray she moves toward healing in her own time and way.