My yearling tried picking up a back leg to kick out once when I put a hose on him. He copped a very fast, very rude shock when he got belted across the backside with a dressage whip and made to run backwards faster than he thought possible. That was 5 months ago, and he hasn't even thought about it since. I just need to growl and make him move away, and he will stand stock still and behave for me.
Small corrections to certain behaviours may work on some horses, but others (most) will need to have a very strong lesson before they click that that behaviour is unacceptable.
Striking, to me, is one of the most undesirable behaviours a horse can have, it is just so dangerous, you NEED to get on top of it asap. Not a little tap on the leg for striking, but a good whack across the chest. If you leave a mark, don't feel guilty. I'll probably get hammered for saying that by the Parelli and 'friendship training' supporters, but I would sure as hell rather give one quick, MEANINGFUL whack across the chest than get my leg snapped in half or an organ ruptured from getting taken out by a striking hoof.
At the moment, it sounds like she thinks you're not serious. She needs to know, in no uncertain terms, that you will not tolerate the striking. If she tried to do the same to a horse more dominant than herself, in the paddock, I can assure you that she would be kicked or bitten to kingdom come and would be thinking twice about pulling the same trick next time.