J.R.
Hi K., I am sort of giggling over here... not because i'm laughing at your plight, but because my son... oh my stubborn little boy! - does this ALL THE TIME. If i tell him no, or he dislikes something, he will throw himself down (not too dramatically anymore) and bang his head on the floor. he will also run toward any wall, door, chair and bang his head on that. he has had a few bruises on his head, and one time even gave himself a pretty good knot that took a few hours to go down since he chose the wrought iron leg of my coffee table to bang his head on.
I was worried at first, because my two older girls did not do this... I asked my ped. and she kind of giggled and said 'let it pass, and dont make too much fuss over him when he's doing it, because it's just getting him attention - if he doesn't get a reaction, he'll find that it hurts a bit and eventually stop', also it's a form of communication since she can't talk yet - she doesn't know how to express 'hey! that's mine! I want that!.
so now when my son does this, i say 'its ok to be mad, but it doesn't mean you get what you want' and i walk away. i can't say this is getting rid of them all together (just yet) but he doesn't have bruises anymore because he's learning to be a bit more gentle on himself. he would lay there and scream - i mean SCREAM. After about 30 minutes i would say, ok, if want to cry, you can do it in your room.
If she does hurt herself, (like my son, who also busted his lip open once throwing his face into the wood floor) comfort her - I sit a few feet and say 'awww, come to mommy, i help you feel better' with my arms open... then i'm not rushing to him, and it's sending the message that things are going to be on my terms, but i'll always be here for him. i always follow up with 'you have to be careful or you will hurt yourself... be gentle, mommy loves you'
Good luck...