We tried a couple of different things, but the combo that worked for us is:
* only give a few bites of food at a time
* if she throws it, don't react. If you need to, just get up and walk away for a minute.
* don't leave her sitting in the high chair for a "few extra minutes" to "just try to tidy up," etc. Once our little guy was not hungry anymore, he needed to be gotten out of the chair, or he'd start playing with the food out of boredom.
Our son still throws food occasionally, but now it's more because he wants something I won't give him (like he wants to play with a toy while eating dinner), and it's usually his sippy cup (which is more dramatic and has a better "thud" factor than food, imo).
Good luck. I know it be super frustrating!