In September 2017, Donnelly announced a major new project with Scholastic Publishing called "Stepsister," to be published in 2019. The story begins where the classic tale of Cinderella leaves off and follows her wicked stepsister Isabelle as "personifications of fate and chance battle for control of her life, hinting that there may be hope after all for a girl labeled "ugly" since her first appearances in literature". Film rights for "Stepsister" are being handled by William Morris Endeavor and a deal is said to be in the works.