J.M.
My all time favorite game that we played at my birthday party/slumber parties as a kid was a clue hunt. My dad would write clues on little pieces of paper and hide them all over the house. He would hand us the first clue that would lead us to the next clue and so on. The last clue would be a "treasure", usually candy, a movie or some little trinket toys. The dollar store would be a good place for this or the clearance valentine holiday racks in stores now (you can get some very cute girly heart necklaces, erasers, pencils, etc.). I have played this game with young elementary kids and up to older middle school kids, and the all love it! Clues could be as easy as pictures or little riddles.
Baking as suggested before is another great idea! Mini pizzas where the girls make their own with their own toppings, bake cut-out cookies (or buy premade) and have a bunch of different cooking decorating toppings set out so they can decorate their own cookies or build your own ice cream sundaes...mmmmm!
I have a 2yr old daughter now and I can't wait for her girly parties when she gets older!!! Good Luck and have fun :) J.