I saw a therapist a long time ago, and she sounds a lot like yours. We basically chatted during sessions, like friends rather than therapist and patient. A really good therapist is not your friend and won't treat you as one. When you look for a new ones, ask the ones you contact what their style is, and I would definitely find one who specializes in BPD. I've read that a lot of therapists actually avoid taking on BPD patients, because they can be tough to work with, so you can avoid what happened with your last therapist by seeking out someone who specifically treats BPD.