Kelly was born in Los Angeles, California. She is the only child of former Aerosmith guitarist Rick Dufay and the late Maureen Dumont Kelly. Kelly and her mother moved to various communities before settling in Chicago by the time Kelly was in junior high school. In 2019, Kelly spoke in an Instagram post about having an abortion, saying "It was the smartest decision I could've made". She has French, Irish and Dutch-Indonesian ancestry.