what are the details of esther's relationship with joan?

Joan Giling is a former girlfriend of Buddy Willard who enters the same mental institution as Esther after a similar suicide attempt but quickly secures her own release from the institution. Nevertheless, the seemingly confident Joan in fact suffers greater problems than Esther. Joan's confidence is simple display; although she appears self-assured, leaving the institution after only a short stay to live with a nurse in Cambridge and even believing that she could become a psychiatrist, Joan is in fact more aimless than Esther herself. After returning to the institution she hangs herself.