The Dying Game — Catherine Johnson

When Shehana finds Vlora, stabbed and dying, on her rough London estate, she stops to try to help her. In so doing, she enters a world completely foreign to her own. Vlora had come to England illegally with her brother to work, and ended up a prostitute. Now Shehana must find Vlora's brother
and, with him, try to track down the killer.
Shehana can't tell anyone what's going on: not her strict parents who want her to work hard at school and marry a man of their choosing; not her best friend, who would never understand; and certainly not her boyfriend. She hasn't even been able to tell him of her secret dream of going away to
university.
It seems that Vlora's brother may be the only one she can talk to. But can she trust him, and what exactly does he know about his sister's life, and her death?