Hi Wolfstar,
I was dx with BPD about 10 years ago. When it was at it's worst though, I was the opposite of your co-worker. I never really acted out, but reacted in. Meaning I rarely would take it out on others but take it out on myself. I never threatened to hurt myself as a way to control the other person or get something I wanted.
Most likely, your co-worker wouldn't be able to tell you why she acts the way she does at times. She doesn't understand what she is feeling or why, just knows that she is trying to find a way to escape from the pain and fear.
Hopefully after her most recent episode, she will be forced to get some help. While that in itself doesn't mean she will recover, there will be someone (either doc or therapist) to oversee her treatment.
This is a good site that may have information that may help:
BPD Central - borderline personality disorder - books, cds, info, support, resources, links