If it were me, I would want to to know exactly what the rules of the group are before I told my therapist. Is there even a remote possibility they would ask one or the both of you to leave or end the group? I've been in groups and the only rule was to maintain confidentiality. But, I know of other groups that have folded or one or both group members were asked to leave. I was in a private therapist group, and the others were connected to private hospitals. Silence may be golden, at least until you know future consequences.

Enjoy your new relationships.