If this other person is saying to your T you have told her something about something your T has done or said to you. That would be very difficult. This is the problem when T's see clients who know other clients. If it is something you have supposed to have said about your T & you it could leave your T in dangerous waters. Perhaps it would be best to find a T and star afresh. Sounds like a kind of sibling rivalry between you & this other client. Your therapist needs to be the adult here and either put it to sleep or tell you be cannot fully trust what the truth is. Im sorry this has happened.