Ingomar, if it were me, I would ditch this counselor immediately. You have very little invested with her, only two sessions, so you should be able to drop her and find someone new with little angst about termination.

I think she was unethical and just plain not a good counselor in what she did. If you don't want to reveal any particular piece of information to her, she should not force you, or play a guessing game, or sneakily try to get the information anyway. She treated you in a way that did not have the good of your mental health at stake. She also violated confidentiality for your friend. She is all around bad news!

I would find it hard to go to therapy with a counselor who knew all about me from another client. Your friend may very well have talked about you numerous times to his therapist, as a woman he was having a relationship with. Your T should not have this information unless you want her to, such as in couples or family therapy.

If it were me, I would explain what happened to my friend and let him know because of this you will not be seeing his T anymore, that you value your friendship with him too much to put him in this compromising position.

If this T works in a clinic, where there is a supervisor, I would report this to her supervisor. She deserves at least a slap on the wrist from someone.