What about a tea party, with all the trimmings? At some of the antique malls, they actually have a tea party/luncheon area that you can reserve/rent, sometimes with period clothing that the participants can wear during the event, boas, 20's-40's hats, etc. You could take each child's picture in their 'finery', maybe even with a polaroid camera so that you can send a good picture home with each child of themselves in costume, separately, and with the birthday girl, a little-girl's best fantasy of a tea party. Only invite 3-4 little girls, to keep it small and cozy. Not sure what this would cost, but the one I went to seemed very reasonable. Check into it, at least. All it needs to be is something SHE will remember (or not, ...though pictures will help). One gift after the fact could be a little album with copies of all the pictures taken during the party.
OR, if you have a friend with a nice porch or deck on their house, maybe you could hold the tea party there, and hit the dollar stores for little special things to wear, a $1. boa, a $1. fancy hat, party favors you find there.
Serve cookies and tea, in a tea set with tiny cups.
Kids that age have no expectations, are easily pleased just to be made to feel special, and their friends the same. It's best not to continually try to one-up the last party, which raises their expectations unnaturally over time. My brother and his wife raised their girls to expect a special party only every other year, with a quiet, family-style simpler part in between, while the sibling is having their special party that year. (The child gets to pick the restaurant, food served, and gets one or two special gifts, no invited guests, low-key.)