Who is Shinko from The Buddha of Suburbia and what is their importance?

Shinko is a prostitute frequented by Changez when Jamila won't have a physical relationship with him. Changez and Shinko become close and Shinko even befriends Jamila. Despite the unorthodox relationship, by the end of the novel she is a fixture in the lives of Changez, Jamila and Karim.