The Specter — Joan Lowery Nixon

Seventeen-year-old Dina is fighting cancer and is  angry at the whole world. But when Julie, a  nine-year-old survivor of a car accident, becomes Dina's  roommate at the hospital, there's no time for Dina  to keep on being angry. Because Julie is  frightened. Desperately frightened. She's sure that someone  caused the accident she was in--someone who will  retum to kill her. Now she's insisting on being  with Dina all the time. But by befriending Julie, is  Dina making herself the target of a dangerous  killer?