Everwild: Book 2 of The Skinjacker Trilogy by Neal Shusterman
Going against Mary Hightower's wishes, Nick, the chocolate ogre is slowly trying to reach every kid in Everlost to hand each and every one a coin, which will release them from Everlost. Mikey McGill and Allie have joined a band of skinjackers who have more of an impact on the living world then any other inhabitant of Everlost. Except Mikey can't skinjack and Allie can - and there is a very good reason.
Allie is not actually dead.