Themes and ideas for a girl's 18th birthday?

My best friend is turning eighteen in ten days. She doesn't want a party, only wants to hang out and have fun.

She just got her license, so we where thinking about jumping in the car and grabbing something just for fun (and of course paying for it!) Other than getting her hair highlighted, we're stumped.

My mother suggested a princess theme (such as doing nails, hair, et cetera.) We also planned to watch Pocohontas (go Disney!)

We could really use your help. Please supply ideas, themes, or anything else you can think of that would be really fun.

Thanks in advance!