The Insider.com

While Kristen Stewart has never come out and legitimately acknowledged the obvious—that she's dating Twilight Saga co-star Robert Pattinson-- a juicy scandal might just destroy the worst-kept-secret romance in celebrity history. 

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Snow White and the Huntsman director Rupert Sanders is at the center of the story, which has People magazine claiming the married father of two entered into a brief fling with his star actress during filming.

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"Kristen is absolutely devastated," a source tells People. "It was a mistake and a complete lapse in judgment."

The source adds, "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."

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Additionally, US Weekly posted a rather compromising photo of Stewart and Sanders, along with an eye-witness account from the photographer who claims the two "couldn't get enough" of each other.

Reps for the director have yet to respond to the articles, and Stewart's rep had no comment.