Dreamland (Riley Bloom #3) by Alyson Noel

ALL I WANTED, ALL I'D EVER DREAMED OF, WAS TO BE THIRTEEN.
BUT THEN I DIED.

Riley Bloom's afterlife is about as good as it gets, except she'll never be a teenager. Riley desperately wants to speak to her older sister, Ever, to ask her advice. Ever is still alive and the only way Riley can reach her is to search for Dreamland -- a place where ghosts can jump into dreams and talk to their loved ones. But when she finally gets there Riley discovers that Dreamland isn't as heavenly as it sounds. In fact, it's a total nightmare.