This is probably not the greatest advice to be giving someone, but in your position I would just tell her to take a hike. It's not her business to determine who you do or don't play for/with based on what
she thinks of the music you play. She's not respecting or supporting you as a son, or even as a human being, if she thinks that she has the power to govern your artistic choices.
Time to put the "big boy" shoes on, with or without her "consent." You are the drummer, not her; if she doesn't like the music you play, she doesn't have or need to listen. Nobody's forcing it on her.
It's a free country and a free world, filled with people who have freewill; you can be in whatever band you want to be in. Do what is right for
you and f*ck anyone and everyone who tries to stand in your way!
