Who is Ruth Sapphira Neumann from Drowning Ruth and what is their importance?

The novel's title character, Ruth is essentially orphaned when her mother Mathilda drowns and her father Carl is in the U.S. Army in Europe during World War I. Ruth is raised by Aunt Amanda, who has a history of mental instability and clings to her as if Ruth were her own daughter. Ruth throughout her life recalls lying under the bed on the island as Amanda gives birth to an illegitimate daughter, and then following Amanda across the ice as Amanda flees to prevent Mathilda from claiming the baby. Ruth and Mathilda both fall through the ice but Mathilda manages to push Ruth to safety before drowning. Ruth always insists that she too drowns.