Kevin, I just realized that your first posts in this thread are from a year ago. I know from my own experience that I am always eager to see responses from other on these boards and it is a bit discouraging not to get some replies. Don't know that I have much if any advice for you. Would you even want her back at this point? Has she gone to anyone else besides a counselor? If she does have a condition like BPD she should probably have something prescribed to address that. Sounds like she has a long way to go before she is ready to commit to anyone or anything.
Focus on yourself and your son at this point and get yourself in a better position. Sounds like your son could really use a good, stable role model at this point.