Kol Isha

Question

Dear Rabbi, I'm a Sephardi that attends the local Othrodox (or what I thought was) Ashkenazi shul. There was a bar mitzvah this evening at Minha / Arvit. BEFORE hamavdil they pulled out a microphone and let an impodestly dressed 14 year old SING Havdalah! I was in shock. I called the Rabbi and he confirmed that she was over 13, that he was aware PRIOR to the singing and totally allowed it. He said "well, it doesn't happen often". I feel terrible and confused. Do I have to do teshuva? Should I even attend this shul any more? Please I need a serious reply as this is a small community and asking a local rabbi could be considered lashon hara. THANK YOU so much for your website and I and my family hope to merit to meet you one day. Regards... D.Y.