If You Find Me by Emily Murdoch

Cary and her younger sister Jenessa have survived on their own for as long as Carey can remember. They live on a broken-down camper hidden deep in a national forest and with their mentally ill mother always away, Carey has learned to fend for themselves.

However, the fateful day arrived when people took them from their home and back to the civilized world of high school, boys and clothes. Carey must learn the truth of why her mother hid them and what must she do in order to prevent her new world from crashing down on her.