Apparently because she is not Chinese she is not allowed to wear a Chinese dress? And because she did she's racist and guitly of cultural appropriation?
I can't see how taking that approach does anything but alienate people and belittle instances of true racism. Where does this lead? What about the evolution of blue jeans with reinforced copper rivets - clearly a part of American history and culture, who is allowed to wear a pair of Levi's? Or if that's different, why?
https://www.thesun.co.uk/fabulous/6174185/american-student-accused-racist-chinese-dress-prom/