Oh please "hit", it was a reflex to her slapping him in the face.
If she's going to act like a man and hit him, then she shouldn't, and you shouldn't be surprised when she gets an equal hit back.
He didn't punch her, he slapped her equally as hard as she did him. Also her slap hit much more solid than his did, and the second he did it he realized what he had done and didn't slap her again, while she went into a rage storm smacking the shit out of him.
I'm glad he slapped her back. Maybe she'll fucking learn a thing two.