How about saying “It’s important to keep being yourself? I know you like boys, but any boy that’s worth liking will like you for yourself and wouldn’t want you to be any other way.” or “I know you want boys to like you, but boys that like smart girls are the best kind of boys to attract. Why would you want to be with a boy that only likes you if you’re dumb and submissive?”

But maybe I just don’t get it because this never happened to me in middle school. I wasn’t liked by my classmates and being smart was one of the few things in school I could derive joy from, so I just didn’t notice or didn’t care. (That and the boys I had crushes on were all smarter than me and I wanted them to think I was smart enough.)