Showing My Book of Life by Angel by Martine Leavitt

When sixteen-year-old Angel meets Call at the mall, he buys her meals and says he loves her, and he gives her some candy that makes her feel like she can fly. Pretty soon she's addicted to his candy, and she moves in with him. As a favor, he asks her to hook up with a couple of friends of his, and then a couple more. Now Angel is stuck working the streets at Hastings and Main, a notorious spot in Vancouver, Canada, where the girls turn tricks until they disappear without a trace, and the authorities don't care. But after her friend Serena disappears, and when Call brings home a girl who is even younger and more vulnerable than her to learn the trade, Angel knows that she and the new girl have got to find a way out.