If I was a therapist working with someone who has had past abuse, I would be concerned about their involvement. Let's be honest, many aspects of BDSM can run very close to abuse and some will try to hide behind it as an excuse for abuse. Like anything, it can be healthy and unhealthy. If you want her to see it in a good light, be transparent. Don't try to sugarcoat your relationship, don't get riled up and defensive, and try to give her as neutral a view as possible. The more you try to "convince" her that it is good for you, the more she is going to be concerned.