I think someone else made the suggestion to block her. I would have advised leaving it alone, but since she is getting on your case about leaving the band I would tell the other bandmates with her present why you left the band while everyone is sober. If they don’t bring it up you can by starting off with “So Buffy has been wondering why I left the band the way I did. I admit I could have said more. Anyone interested? Warning not everyone might like what I have to say”.