My ten month old does this, too. He actually loves to THROW his sippy cup across the room. But he also drops food, and then looks to see where it goes. Or feeds it directly to the dog.
Fun, huh?
By 14 months, I think your little one is ready to understand consequences a bit better than my guy. I'd tell her "Oh, are you done? Then I'll take that." Then clear her tray. If she's upset, then offer her a smaller snack and say, "If you drop this, dinner's over!"
When she drops it (which she will!), then take it away, and take her out of the high chair. I bet she'll figure it out in a few days, and she won't starve! I'd pick my battles, though. As long as she's eating while dropping, I'd let her drop without comment. Only take away her food when she's dropping for fun, with no eating at all.
Also, I'd let her use the spoon. My son isn't great with a spoon himself, but he's already learning to dip it in yogurt and put it in his mouth. Messy as heck, but he's learning! Your little girl is probably ready to play and learn this way, too. But yeah, it'll end up on the floor too.
PS It is pretty funny, isn't it? I love that look on my son's face. Over and over- like he's thinking, "Wow, gravity still works!" :)