The Girl of the Limberlost (1945)

Elnora Comstock lives on the edge of a great swamp and collects butterflies to sell in order to go to high school and pay for violin lessons. Her mother, Kate Comstock, hates her as she blames the girl for the father's death as he drowned in a quagmire on the way home the night the girl was born. The years-late revelation that the husband had been off courting a neighbor woman that night brings an attitude adjustment to the mother.