Was I in the wrong to bring this up to her?

I dont think you were really in the wrong.. shes probably just sensitive, I mean whether she was wrong or not, no one likes to be told they are doing something wrong. especially considering shes had a lot of crap happen to her lately, I can understand she doesnt want to be a part of something that makes her feel worse. even if she WAS technically in the wrong. Its really too bad that there is drama in the group and now you guys are short one person, but pointing fingers doesnt really do any good. just dont let it make you feel guilty.. besides, whats done is done. maybe you can find a new member to fill her place? and make sure you make it extra clear to anyone new that joins your group what the rules are but also keep in mind that they might not be perfect and to think twice before correcting them if you want to avoid hurting their feelings.