Who is Jessamine Stevens Edwards from --and Ladies of the Club and what is their importance?

Jessamine Stevens Edwards is John's cousin's widow. She moves to Waynesboro because Rodney, her son, suffers with malaria. Anne is certain, however, that Jessamine once had an affair with John and that Rodney is actually his son..... not John's. Over the course of the novel, Jessamine marries Sheldon Edwards.