Stewart was born in 1990 and raised in Los Angeles, California by parents in the entertainment industry. Her father, John Stewart, is a stage manager and television producer who has worked for Fox. Her mother, Jules Mann-Stewart, is originally from Maroochydore, Queensland, Australia. She is a script supervisor and has also directed a film. She has an older brother, Cameron B. Stewart, and two adopted brothers, Dana and Taylor.
Stewart attended local schools until the seventh grade. As she became more involved in acting, she continued her education by correspondence until completing high school.