Mother Sister is a character in the film Do the Right Thing, portrayed by the late Ruby Dee. She is an older black woman who observes the neighborhood goings-ons from the window of her brownstone and despises Da Mayor.
She is first seen when Mookie briefly stops by Mother Sister's window, and gives him advice. She is seen again when Da Mayor is drinking in front of her brownstone and insults him for being a drunk. Then she is seen on the steps outside her house when Jade combs her hair, to which Da Mayor says how she has beautful hair.
She is later seen when Da Mayor brings her flowers, but doesn't talk. After Da Mayor saves Eddie from the car, she praises him at nightfall while on the steps.
When the riot starts, and the pizzeria is burning down, she yells: "Burn it down! Burn it down!" But when the fire fighters spray water at all the black people, she repeatedly shouts: "NO!", and Da Mayor goes to comfort her.
The next day, Da Mayor is shown being awakened by Mother Sister in her house. She says how he almost got himself killed the night before, and that she couldn't sleep.