Sorry, without more details about Mary Deerfield, it's difficult to tell the true story. Maybe she is a local figure in a particular area or involved in a specific historical event. If you can add more information like the time period or her occupation, it would be easier to answer.
As I don't know the exact Mary Deerfield true story, I can't say for sure if there is a book or movie about it. There are so many stories out there, and if it's a very personal or local story, it may not have been made into a book or movie yet.
The truthfulness of the Mary Stauffer story can be a complex matter. It could involve elements of truth mixed with creative interpretation or exaggeration. More investigation is often required to establish its authenticity.
I'm not sure. It depends on the context and the source of the story. Sometimes stories like this can be based on real events but have fictional elements added.