Because people are racist. People think 你 can act black when there's really no such thing. 你 can't act like your race. So the people who call her that are mean. As for the Nicki Manaj thing, its because of Iggy's abnormally big butt and Iggy's rap style is similar to Nicki. But its all not true.
idk because I think she has a natural talent and so has so much potential and shes using it and shes so beautiful and I don't think shes trying to act like nicki manaji