my son just had his first birthday party in July and it was a big hit. His favorite things, then were balls and bubbles. So, we had a bubbles and balls party. At this age they can't handle a lot of structure so our activities definitely were not structured. I just collected all kinds of different sized balls preceeding the party and dumped them all out at once for all the kids to play with. They LOVED it. After that I passed out all kinds of different bubble blowing devices to the parents and older guests and we blew all different sizes of bubbles at them. It was really a lot of fun and the kids really enjoyed it. I made the invitations also, in a circle shape (because balls and bubbles are circular). I got the template from the martha stewart website (the kids magazine link). She has some really good ideas on her site. I baked the cake in a bowl so that it was round like a ball on top and cut all the kid snacks into circular shapes. Sorry, to be so wordy, I obviously enjoyed doing his party. I would just find a couple of things that your daughter is really excited about right now, and make that your theme. Its so much fun to do, really. Enjoy it.
J.