D.N.
Baby powder. Sprinkle baby powder in her hair and scalp. It makes it very easy to get that sand off. I read it in a magazine this summer so took a container with us to the beach. Many, how I wish I had known it worked so well last year. I was able to brush the sand right off of myself and kids--nad they smelled nice. : )
Then all you have to do is brush her hair really well and wash.