I think these silly not hitting girl rules are kind of dumb. Not that girls should get hit it's just that it should apply the same way to females. Being a girl I have never slapped or hit another guy in a serious manner. Maybe a jokingly friendly punch in the hallway, but nothing more then that. So I don't always understand people who regress back to child like ways of dealing with problems.
I really hate the whole if a girl slaps a guy in the face he must of did something to deserve it, but if a guy slaps a girl in the face IT'S ABUSE. I guess the point I'm trying to get across is that I'm not some piece of glass that is going to shatter the minute a man punches or slaps me. In general yes males are stronger then females, but I wouldn't just curl up into a ball and scream and run around the house like movies and television always presents it.
Furthermore be it male or female if you are regularly hitting either gender in a physically meaning to hurt violent way then there is something wrong with you and you need to get help. It's just not excusable because you are a girl.
Anyways self defense is fine by me whether it involves males or females doing the defending. No one deserves to be slapped or punched and no one deserves to just take it because society thinks it's okay.