my ds is 13 months, and just starting to do the play with food thing. I guess we've decided what we find acceptable and what not, and we are enforcing a couple of rules. eg, he only eats in his high chair, that way the rest of the house doesn't get covered in food, and it is all containted, plus, he associates food and place.
I also hate the tip the plate over your head routine, so when he does that, I take the plate away and put his finger food piece by piece on his high chair tray. He hates that because he likes to play with the whole plateful. After a few minutes I give hime the plate back....until he puts it over his head. He is gradually learning that if he wants to play with the whole plate, he mustn't tip it over his head.
I do let hime play with his food on his high chair tray as much as he likes (half an hour of spreading jelly everywhere was very entertaining for him, and peaceful for me! I think playing with food is part of learning about it and enjoying it, so I try and let him do it, but have a couple of rules, so that he knows it isn't a free for all.
I guess what I'm trying to say is, decide which bits are important to you, and enforce those, and let the rest go. I agree with twiglett, I think you can exhaust yourself trying to make it into a game, once she's had her food there for 20 minutes (or whatever) what hasn't been eaten isn't going to be eaten, so call it a day.
I know for myself, that the more stressed I get, the more he mucks around with his food, I think he knows that he is having that effect, and since I decided what I am happy to let pass, we've both enjoyed meal times more.