This Life is a Beautiful War

Jake Macpherson and Gabrielle (Gabby) Arnold had been best friends since preschool. But then Gabby was in a car accident when she was twelve, which killed her father. Jake stuck beside Gabby through everything, though, even when she tried to push him away.
Now it's their senior year and Jake still knows that Gabby is keeping something from him after all these years, something that she tries so desperately to hide by never wearing anything that shows the skin on her arms or legs.
That is until one day she finally breaks and Jake finally finds out what's been happening to her.