Amanda Seyfried has opened up about the difficulties of dating Dominic Cooper, insisting she hated knowing the British actor was shooting romantic scenes with female co-stars while they were apart. The Les Miserables actress began a relationship with Cooper after they played a couple in 2008 movie musical Mamma Mia!, but they were often in different countries due to their busy work schedules. Seyfried admits it was torture knowing Cooper was getting close to his female castmates, and she still has her suspicions about rumours he cheated on her with Irish actress Ruth Negga, who is now his girlfriend. In a candid chat with U.S. magazine Allure, Seyfried explains, "That was hard, knowing he's going to make out with Keira Knightley or the girl he's now dating (Negga). I was in Ireland and the Daily Mail article came out and he was caught with his co-star. "To this day, he says it never happened, but now they're dating. You know what I mean? He is one of my closest friends still, but that is what's hard about dating an actor." Cooper was first linked to Negga after they appeared together in West End play Phaedra in 2009.