It's because blood rushes to her face.
Why does a girl blush if she hates a guy?
Who says she's blushing? Maybe she just put on too much makeup.
blush: A reddening of the face especially from shame, modesty, or confusion.
It's a response that we can't control. It has numerous causes.
That is not a blush, it is a flush. Blood rushes to the face in anger.
playing hard to get.