Griffin grew up in Scarborough, Ontario. Her mother was a teacher, and her father was an air traffic controller. When she was 8, she played the role of The Artful Dodger in her school play, which garnered notice from her mother, who was the school director, of her talent. Looking back at that period, Griffin said that she was more inspired by watching movies than theatre, especially concerning strong women, and cited her mom as a huge influence.