Who is Sarah from A Shining Affliction: A Story of Harm and Healing in Psychotherapy and what is their importance?

Sarah was one of Annie's closest friends. It was Sarah who helped to arrange Annie's surprise birthday party shortly before Annie had her break down. Sarah helped Annie's sister, Mary, take Annie to the hospital. It was also Sarah, along with Mary, who picked Annie up from the hospital and took her to the house where she will be staying. Later, it was Sarah who drove Annie to and from her appointments with Blumenfeld. Sarah initiated the tradition of brining coffee and donuts for the two to enjoy on their way to Annie's appointments.