Contrary to the assumptions of many, you don't have the ability to control mom. Also I don't buy the notion that "she's trying to turn everyone against me". Red flag there.
The only reason it's a drama for you is that you're making it so. If you're not in high school anymore, then don't act like it.
I've been in a bunch of situations where people don't like me and talk it up to everyone else. The best thing to do is give it the attention it deserves. Zero. Treat you bandmates well (and the daughter) and I doubt much will come of it.
Unfortunately, I don't think this is one of those "ignore it and it will go away" types of issues. Sometimes, an adult has to tackle issues head on. When someone is trying to sabatoge your hard work, and has the ear of those to have a direct impact, it can't be ignored.
