Question: does maddie die at the end of everything everything

Answer: No, Maddy's mother, after therapy, reveals that right after Maddy's father (a police officer) and her brother died, Maddy got very sick, and her mother, not wanting to lose her, decided she had SCID, and needed to be kept away from the world. In the end, Maddy and Olly happily reunite in New York, where she sent him on a mini scavenger hunt in a used bookstore.