Rage, by Jackie Kessler, is her second book in the Horsemen of the Apocalypse: The Riders Quartet. Like Hunger, the first book, Rage revolves around a teen who harms herself as a means of controlling her emotions and dealing with those events in life that she can't control.
And Missy's life is on a track that she can't control at all. After a disastrous party, Missy takes the cutting too far. As she lays dying on her bedroom floor, she's visited by Death (who looks suspiciously like a dead grunge star). Death offers her a choice: die or take up the ridership as one of the four horsemen.
As Missy assumes her position as War in the Quartet, she learns how powerful not only anger, but all emotions can be, and how to marshall that anger into something that isn't as destructive as cutting. Despite the dark themes, there is humor and hope in this series and while the book doesn't close with an easy, neat "happily ever after", it does end with the promise of redemption & healing.