Don't be upset, you shared with your T how that is unacceptable, she admitted she didn't realize (do you use different last names I suppose?)... and that should be the end of it. He should have a different therapist from now on. She sounds like it was a mistake and she would not have done the intake had she known.

It's a good thing though, imo. Your T got to see your spouse/ex to be? in a way otherwise not?

I know that during the course of some of my treatment, prior to my divorce, my then spouse demanded to see my T... and whoa! as cunning as he thought he was, my T saw right through him! (My T didn't share much more than that until many years later.) It was good to hear from my T how he understood some of my difficulties having met my tobeex, it validated my view of things. (When he met him we didn't realize my tobeex was planning divorce... ) There was no way I could even begin to progress in therapy while still in that household with (ex)!!!

It would be unethical for your T to also counsel your spouse in this situation imo, and it seems she realizes you don't want her to either.