The best way to deal with passive aggressive people is to be upfront, honest, polite, and loud and clear. You should have said to her something like “Excuse me. Do you have a problem with me? Because you are jabbing at me all of the time and not in friendly way”. If that behavior doesn’t stop, you reply back to it 2-3 more times. Then you have a band meeting to discuss the problem. Then you leave the band letting them know why. It is still not to late for them to know. Especially since she is dumping on you for leaving the band. So called friends roasting on each other is most common among adolescent boys. Adults who continue that practice tend to be emotionally inept adults. They are incapable of expressing friendship or being friends without using insults. I had a job on a break from college working in the loading dock of a big department store. This kind of adolescent behavior happened all of the time. I greyrocked it all until one day I got tired of it and returned in kind. The guy who I insulted back got pissed, jumped on me, and others had to pull him off. Don’t believe the BS “it is all in fun!”. Stand up for yourself when it happens. Let people know it isn’t appreciated. If that doesn’t fix it move on to a new crowd of people.