What is the role of Esther in Mary Barton?

Esther's role is that of a mentor. Her purpose in returning to Manchester is one of experience and love. She is determined to save Mary from her own mistakes..... to guide her on a happy path and reveal the effects of her own choices. Esther, herself, is a lesson for Mary. A lesson that teaches the consequences of following one's emotions rather than following the direction set out for her from birth.