as an oft-bullied AFAB person: girls will pick on you if you don't have the right hair or the right clothes, obviously, and also for hanging out with boys, trying 'too hard' at looking pretty or doing something, not trying 'hard enough' at looking pretty or doing something, being socially awkward, being literal about things, reading a lot, enjoying school, and I think that's all I can think of. admittedly this is early 2000s stuff, but I think some would apply across the board--like the first one. also, the way girls bully is more...subtle. they pick on your clothes, but with backhanded compliments. they tell you you're stupid, or that you don't pay attention enough, and that's about as direct as it gets, outside of tripping you in the hallways once in a while. they'll talk behind your back, spread rumors--that sort of thing.