I would feel very much like you do. I participated in a trauma group a while back, and a close friend showed up one day. As soon as the T found out we knew each other (even though we had met in a dbt group), my friend was asked to leave and put on a waiting list for another group. I would think that is pretty standard for therapy groups. I have been to groups where I knew people, but it had always been that I met them while in treatment and that was the only way we knew each other. Any time I had known anyone more personally the newest member of the group was moved out. I'm wondering why the T would not be concerned about any relationships, especially if all business should be restricted to group. I know most groups operate under confidentiality agreements, but even so, with members that are likely to have interactions outside of group, I would think that the T would take steps to find a different group for the incoming individual...
I hope things get resolved for you. (hugs)