It wasn't a breach of anonymity, but the original poster described it as a "breach (breaking) of confidence". There's a big difference and I would, too, be a little annoyed. AA'ers are not only alcoholics with all the character defects that go with that, but unfortunately AA-ers do exactly what normal people do in organizations and clubs. They socialize and sometimes talk about other people.
I think the talk was harmless and sounded positive, but I don't think your sponsor has the right to talk to anyone about your progress and step work.
I would tell her so. It might be a good time to clarify who she is going to discuss you and your step work with. My sponsor informed me in the beginning that she would be discussing me and my step work, for advice and direction, with her own sponsor and if that was okay with me. It was, and it felt interesting knowing that occasionally there was not one but two people trying to drag me into the lifeboat.