I'm a victim of mean girls, have been at school and later on in life.
Sometimes though I think mean things about them and about other people though I don't do anything about it, I don't treat them mean. I might just think they are annoying or that colour doesn't do anything for them or I just don't like them but I'd never verbalise it.
AIBU thinking that everybody does this to some degree however small and to say they don't is disingenuous,