Former Twilight star Kristen Stewart reportedly cheated on boyfriend Robert Pattinson with a married director.
The alleged affair apparently happened recently, sources have told People magazine.
The Twilight co-stars relationship is said to have been rocked by the startling claim.
"Kristen is absolutely devastated," one insider told the publication. "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."
Kristen, 22, and Robert, 26, seemed to be in good spirits just a few days ago at Comic-Con and were seen laughing and joking together.
The pair has been dating for several years after getting together soon after production started on the hit vampire franchise.
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