Waiting for Normal by Leslie Connor

Twelve year old Addie's parents' recent separation has split not only her father-in-law and mother, but Addie from her step-siblings. A driving force between the break-up is likely whatever mental illness drives her mother to spend all her waking hours on the Internet looking for "business opportunities". Dwight, the step-father, has without obligation sprung for a yellow trailer in the city in which mother and daughter will live, and sends monthly checks that usually catch flight once they're in "Mommers'" hands. At a service station across the street friom the trailer, Addie befriends Soula and Elliot. Soula is in chemo, and Elliot dates the owner of a local restaurant. When her mother's business opportunity finally arrives, Addie is often left home alone for days on end. She even resorts to packing empty cereal boxes with thumbtacks to cover when her grandfather comes over to check up on her. She has managed to mature beyond her years, but maturation isn't enough to avoid a terrible accident that will eventually alter her and her family's way of life.