Who is Milly Jones from Absalom, Absalom! and what is their importance?

Milly is Wash's granddaughter. She is fifteen-year-old when Sutpen seduces and impregnates her with the intent of fathering a son. When Milly has a girl, Sutpen is badly behaved and insulting. As a result, Wash kills all three..... his granddaughter, great-granddaughter, and Sutpen.