Spearritt was born in Great Yarmouth, Norfolk to Michael and Jenny Spearritt, growing up in nearby Gorleston-on-Sea. She is the youngest of three children. Her sister is former model and fashion designer Tanya Spearritt. Her uncle, Eddie Spearritt, from Lowestoft was a professional football player who played for Ipswich Town in the 1960s. At the age of three, she featured in a Mothercare catalogue.