How can I stop my friend from slapping me?

my friend used to slap me...i don't know why. she'd just do it, then one day i hit her really hard, then i went home and left her a comment on myspace & i was like, "i hate when you slap me! you need to stop! its vicious and painful!" and then we talked about it in person, and she stopped? haha. i guess you just need to talk to her.