C.M.
What about a Nines Party? Have her invite 8 friends (so 9 total) and come 'dressed to the nines'? Have everything revolve around the number 9. Maybe do 9 activities?
1. Craft (maybe all make 9 necklaces with beads or something?)
2. Ice Cream with nine choices of toppings
3. Movie at home (at 9pm - if that is not too late)
4. Candy Buffet where there are nine choices (goodie bags for girls to take home)
5. Each girl can make a scrapbook page for your daughter and have number 9's cut out for different decor on the pages
6. Scavenger hunt to find 9 things
7. Paint each girl's nails 1 of nine colors (or 9 of the 10 fingers a different color)
8. Buy nine books/girly magazines and give one to each girl to read/cut out and make some sort of collage. Or just reuse old mags and have each girl make a 12x12 page of "What I want to be when I grow up" or something with 9 different cut out pictures (they could take this home)
9. Have a 9 option breakfast buffet at 9am the next morning (if doing a sleepover).