This is JMO...i was diagnosed with BPD in my 20s. Now 49, sober for a good many years, now in the program and considerably mellowed out. I look back on myself in this period, and the way I am now, and I almost don't reognize that person. Borderlines tend to mellow with age, and I wouldnt relive my 20s for any amount of money.
My heart goes out to you, and to her, too. Despite her cruel act of sending you that photo, she is in a lot of pain--pain that you can't ease, and that she will drag you into.
Sounds like you're getting very wise advice here. Might I add: Please take care of yourself first. You cannot help her.