Who is Joyce Barnhardt from Four to Score and what is their importance?

Joyce Barnhardt is a woman that Stephanie has known since they were both little girls. Joyce was a bully in school, always making fun of Stephanie to the point of humiliation. Later, when Stephanie was married, Joyce had an affair with Stephanie's husband. Stephanie dislikes Joyce. Stephanie's cousin is aware of this situation, but decides to hire Joyce as a bounty hunter anyway. Not only this, but Vince gives Joyce the same case Stephanie is working on, Maxine Nowicki. Joyce begins to follow Stephanie so she can steal Stephanie's leads in the case. Later, Joyce shows up while Stephanie is arresting Maxine, giving Maxine the chance to escape. However, Stephanie manages to get the jump on Joyce later in the novel, making the arrest while leaving Joyce abandoned in her car.