Sydney Sweeney couldn't resist expressing her love for costar Amanda Seyfried while filming their new movie, The Housemaid. The Euphoria star, 28, revealed on the Monday, December 1, episode of The Tonight Show Starring Jimmy Fallon that she is a huge fan of Seyfried's role as Sophie in Mamma Mia!, which is based on the hit ABBA-themed musical of the same name. "Did I know Amanda before this? I'm obsessed with her," Sweeny responded when host Jimmy Fallon asked if she knew Seyfried, 39, before working together. "She knows how much I am with her. I am like the biggest Mamma Mia! fan.