Hi L.,
In the past, I have had my son's parties at home to save on expenses. We have the old fashioned games I had as a child (with a twist, of course)... we had relay races, games, and making their own party hats. We revised pin the tail on the donkey with pin the spatula onto Sponge Bob's hand. You can keep the food fairly inexpensive such as sloppy joe's, chips, finger jello, etc...
This past birthday, my son wanted to have his party somewhere other than home (as many classmates do). I used the excuse of his golden birthday to keep the cost down (he had a bowling party). I told him it would be ok, but he could only invite 8 friends because it was his 8th birthday. They had a blast, but he's talking about having his next one at home so that he can have more friends over (it was hard for him to choose just 8).
With my son being my oldest, I'm trying to pay attention to what the other families do. I can't however "keep up with the Jones'". Ideally, I would like for him to have 2 to 3 friends overnight and just play + have fun. We could let him choose his favorite foods for supper and let the kids decorate the cake. I think that would be fun and much less expensive. So far, it seems like there are fewer parties this year (he's in 2nd grade). Seems as though K + 1st there were more parties... although we're only a couple months into the school year.
There didn't seem to be issues with only having 8 invited this year. Usually it is either the whole class or just the boys (or in your case, just the girls).
I don't know how helpful I was, but this is what we have done so far.
Hope everything goes well for you and your party planning. Wish your daughter a "Happy Birthday".
~SR