My therapists are my advocates. I trust them, or I wouldn't have told them all that good stuff about me. Sharing information means that they have a more complete picture of me. That's good.
They need your permission to share information. If you are nervous about what they might say, ask them what information they want to share. "Hey, Dr. A, what information do you want from Dr. B?" "Hey, Dr. B. Dr. A is going to ask you XXX about me. What will you tell them?"