I was driving my daughter and her friend recently and the friend (who is 9) started making fun of an Asian person speaking like that and I immediately said “NOPE, that’s racist, we don’t do that.” They tried to backtrack and I just said “I heard you and it’s wrong and you don’t ever do it.” I said it pretty forcefully and they both looked scared so I hope it made a big impression. I’m sorry your daughter had to deal with that.