I'd go with professional advice.
She went into a rage when you confronted her about her past relationships. How much more would that be attacking her as a person? That is likely how she would see it. She's already under care and on meds for something besides BPD (depression? Anxiety?).
forcing my Ex to confront her past relationship problems
The problems are the symptoms, not the cause. She likely feels great sadness and shame over failed relationships. PwBPD feel shame at their cores "I'm worthless and unlovable." I've seen significant others be committed for psychiatric care. It usually follows a significant outburst (violence, suicide ideation), and rarely does it help other than on the short term though we do have a few success stories within marriages and with parents of children with BPD. Even those required significant support from loved ones.
I feel that you want to support her because you care about her. Given that she's shown that she can be violent, however, you need to protect yourself.