Who is Sylvia Moore from The Concrete Blonde and what is their importance?

Sylvia and Harry have been a item for at least a year, seeing each other three or four nights a week. She loves Harry and makes no secret of it. She is an attractive woman with shoulder length, dark blonde hair that the sun can make look like gold. She had lost her husband, a narcotics officer, to an apparent suicide, which Bosch had been assigned to investigate, and their relationship develops from there. Bosch still sometimes feared that she would wake up one day and realize that he was just a substitute for the husband she'd lost. Her body is tanned and young looking, thin with small breasts. She has a flat stomach, and her chest is freckled from overexposure to the sun. At thirty-five years old, she is a teacher who is well liked by all who know her.