The relationship between Kristen Stewart and Robert Pattinson has been rocked by claims that the actress had a brief fling with a married director. Stewart’s hookup with Snow White and the Huntsman director Rupert Sanders – who is married and has two children – is believed to have occurred recently. “Kristen is absolutely devastated,” People magazine quoted one source as saying. “It was a mistake and a complete lapse in judgment. “She wasn’t having an affair with Rupert. It was just a fleeting moment that shouldn’t have happened. She never meant to hurt anyone. She’s a good person who just made a bad choice,” the source said. Meanwhile, Us magazine revealed on Tuesday that it’s set to publish photographs of a “marathon makeout session” between Stewart and Sanders. It said that the 41-year-old and his dark-haired woman were caught in a series of clinches on July 17 and “it seemed like they couldn’t get enough.” The 22-year-old actress and Pattinson, 26, were all laughs just days ago at Comic-Con, even joking about their on-camera smooching scenes. The couple met on the first Twilight set and reports began almost immediately that they were a couple.