I know this is hard to do but you must IGNORE her. My son did a few times throw himself onto the floor and bang his head but becuase I walked away without comment he quickly realised that he wasn't getting what he wanted and nor my attention! Hence this trick didn't last very long. The more you or anyone else make a fuss she will do it all the more. Toddlers are very good at putting on the dramatics in order to wrap you round their little fingers! What's more is that these behaviours are completely normal!
The other tactic is to try and avoid any tantrums by distracting her with something else. Good luck

My son was about the same age when he started head banging. He'll bang into furniture or on the floor - it's all about attention. Make sure she can't fall and hurt herself, just lie her on the floor and turn your back and walk away. The minute she's quiet, give her some attention and distract her behaviour. Good luck, they do get over this stage.