What to do with a "Tweener"?

Last night our family was invited to a Christmas party by some friends from church. They were having a white elephant gift exchange so we explained in detail what that was as to avoid the disappointing sighs after opening their gift. I also explained that most every one there would be adults so the gifts would not be for kids. We also told them that the gifts were usually silly junk that people found around the house. As the night ended, Abby got a shoe box filled with stuff from someones junk drawer (old candy, dice, an old wallet, plug in adapter, squishy ball ect..) Jared got an old palm pilot and Molly got a bag with a can of Comet, scrub sponge, dusting spray and a candle. Molly pouts all the way home and goes straight to bed after getting home. I go in to check on her and she is crying because it was "so unfair" what she got. She will be 11yrs in a week and a half and she is acting so pre-teen! She has been acting as if life is all about her and we are here on the earth to make her happy. We have not even gotten there yet and I think the teens will be the death of me. Are boys like this too? Is this just a phase? How do you get a kid, dealing with hormones, to stop being selfish and self-centered? Unfortunately, I'm sure she has learned it from the best. Ouch!