Who is Helen Stone, Ruth's mother from Housekeeping and what is their importance?

Helen Stone is Ruth and Lucille's mother. She left home when she married Reginald Stone and was soon abandoned. Her daughters had no memory of their father. As a single parent, she provided for her family by selling cosmetics in a drugstore, while a neighbor watched the girls, but in many ways she is also an absent parent. Ruth remembers her mother ignoring them for long periods of time and suddenly looking at them as if surprised to remember their existence. She drove off a cliff to her death when Ruth was about six years old.