I had a situation where a friend of mine told me some information about her familiy that was very sensitive and potentially devastating. I found out she knew my T through her ex. I needed to talk about this in therapy and first kept it anonymous but finally spilled the beans about who I was talking about. It was OK, because I trust that whatever goes on in the room between me and T, stays there.

Your T invited you to speak only after you told him you knew the other client so would he invite her to speak if she didn't say anything? How would it feel if you asked him not to discuss you with her? Could you trust him to do that? Can you tell him what you told us...that you would consider it a violation? I hope you can talk this out with him because it sounds like you have done a considerable amount of work together already.

T's have an ethic to protect each client's privacy. If you have been with him for this long, then your safety is of the utmost importance. Good luck.