A breach of confidentiality is huge. Strict confidentiality is the bedrock upon which therapy lies, and I expect my therapist to adhere to it at all times. It wouldn't matter if she was talking to my doctor or trying to be helpful or whatever. I might talk to her about it, but it's hard to imagine an explanation that would make breaking confidentiality okay, aside from the exceptions provided by law (mandatory reporting of ongoing child abuse, etc). This isn't at all the same thing as a misunderstanding or moment of misattunement or whatever. This is a serious breach of trust and professional ethics, and it would always be in the back of my mind that this therapist thinks it's okay to talk to other people about the things I share in session. I would leave.