I believe your behavior was improper.The woman very likely is merely ignorant; possibly stupid, and she may have been "jabbering" away loudly as an attempt to gain attention because she's lonely and feels unwanted. True, she interrupted your performance and the other audience members, but being oblivious to her surroundings and having undiagnosed steatopygia, in and of itself, does not mean she meant to do harm. It is highly likely that you greatly embarrassed her in front of her peer group, and you should feel embarrassed as well for not handling the situation in a more gentlemanly and professional manner. Or maybe ditch the Christian hymns from your repertoire so as to not appear hypocritical when you behave as rudely to others as they behave rudely to you.Please give thought as to how you might in the future better handle the occasional challenge to your professionalism. You asked - I answered.
I also agree with you..
I'm thinking that it's a purely (in the moment judgement call)...
Best to see if the band keeps you or replaces you as there drummer..
I say this tongue n cheek, but it happens...
Either way...hindsight is 20/20.....forgot about it & see what surfaces from yr bandmates.