I recommend a spa party theme if she's "girly".
You can make face masks out of yogurt and honey, avocado and lemon, etc. Serve finger sandwiches, and have a nail painting station. You can also make cheap hair curlers from an old t shirt. Simply rip/cut 1 in by 5 in strips from the t shirt, you'll need about 15 for one head. Take small sections of damp, but not dripping wet hair (spray with a bottle), twist together, and wrap around the strip of t-shirt. After rolling up the hair, tie off the t shirt so it stays in place, and spray hair spray on finished curls. Sleep on the curls, and in the morning, wake up to perfect ringlets. For party favors, I recommend cheap, but not necessarily inexpensive nail polish or makeup from a local walgreens/CVS. Walgreens carries a nail polish line called "sinful colors" that are $2 a piece, and they have a lot of sparkly, fun colors.
Hope that helped.