Curious to see how the community responds to this. I'm going through a similar situation with a half-sister. In our case we didn't break off the relationship -- we moved forward which has created its own set of challenges.

My own feeling is that counseling for this issue is kind of a crapshoot for the simple reason that clinical awareness of GSA is severely lacking. Medical studies are few and far between. Generally speaking, mental health professionals aren't trained to deal with this. Some will attempt to force the square peg into the round hole by applying a well-established standard of care for abusive incest to adult/mutual situations like yours and mine which are most definitely not the same thing.

I'm truly interested to see all the responses here. Good luck.