Both actions were wrong. So many on this thread insinuate that it's ok for the girl to not get in trouble because the real point is that you just don't hit girls. Ever.
Why do the two actions have to be mutually exclusive? It doesn't have to be one or the other. It's completely inappropriate for a man to hit a women. Ever. But it's also just as lawfully wrong (not morally wrong IMO) for a woman to hit a man. But a woman should also be charged with assault just as a man should, if she punches some guy in the face (unless it's obvious self defense). Luckily for the woman, many men would end up dropping the charges anyway if a girl hits them.
We live in a day where women feel like they are fighting for 100% equality with men. They feel like this is a mans world. Well, until incidents like this are handled the same for women as they are men, things will never be apples to apples with men and women. You can't protest for women and the priesthood on one street, and then conveniently skip the protest for domestic violence punishment equality between man and woman that could be taking place on the next street over.