Who is Mysterious Woman from Manual of the Warrior of Light and what is their importance?

The mysterious woman appears to the boy on the beach and teaches him a very important lesson about patience, faith, and learning what is important in life. It is never revealed whether she is a real person or an apparition because once she appears, she disappears as fast as she came. She is only there to offer wisdom to the boy, then to motivate him to write the book when he is a man.