Who is Sarah / Angel / Mara / Amanda from Redeeming Love and what is their importance?

The protagonist of this story goes by many names, and each one is significant to her character as well as to how others view her. First, as Sarah, she is a young girl. She lives with her mother, Mae, and their employee, Cleo. Much of her personality and opinions are formed at this young age when she learns that her father doesn't want her and that her mother would get rid of her if it meant keeping her father around. When her mother dies, Sarah is sold into prostitution at the age of eight.