This is exactly the problem. You see the little faux blush she does at the end of the rap? The covering of the mouth, the manufactured flushing? Fake, fake, FAKE!
She knows she nailed that rap. She flipped it on some theater kid shit and killed it, and she would never have sprung it without 500 hours of practice, trying to capture the authentic hiphop delivery that hip hop artists have. She didn’t capture it, but she knows her audience doesn’t know that, so for all intents and purposes, she macked that, and she knows it.
She’s phony, and that clip shows it.
But! Phony is good in Hollywood. I believe that most of the haters will succumb eventually and learn to let the hate roll of and fall in love with her again.