How do I get over my best friends death?

On February 20, 2011, my bestfriend was in a awful car accident. She died on the scene. As you can imagine, she was mutilated. Her casket was open anyways, and it was awful. It didnt look anything like her. Every time I close my eyes, that image pops up in my head. She was only 14. I can't handle this, and I fel depressed all the time. Sleep isn't even an option for me. How can I move on?