I see where that would concern you. She might know about you, but, especially if she's at the level where she's supervising other T's, she should be able to keep that information out of your marriage counseling sessions. I mean, I've told my marriage counselor some stuff directly (like over e-mail or phone) and he's kept it out of joint sessions unless I told him it was OK to bring it up. So she should be able to keep that knowledge locked away in her brain and not mention it in session.

Also, I'm not sure how supervision works, if the T still keeps the client anonymous. It could be the supervisor knows that one of your T's clients had that experience, but doesn't know it's specifically you. Does that make sense? My T and MC don't actually have supervision (both very experienced), but they have weekly staff meetings where they sometimes will share something going on with a client to get feedback, but they keep it anonymous.