Kristen Stewart Cheated on Robert Pattinson with Married Director » Gossip

Robert Pattinson and Kristen Stewart

Kristen Stewart Cheated on Robert Pattinson with Married Director » Gossip - Kristen Stewart and Robert Pattinson seemed like the perfect, albeit incredibly private, young Hollywood couple. But the strength of their union has been called into question by reports that Kristen may have cheated on Rob with her married Snow White and the Huntsman director.

People is reporting that Stewart had a brief fling with director Rupert Sanders recently. "Kristen is absolutely devastated," a source told the magazine. "It was a mistake and a complete lapse in judgment."

Sanders, 41, is married to British Vogue model Liberty Ross, with whom he has two children, ages 7 and 5. His rep could not be reached for comment about the reported infidelity.

"She wasn't having an affair with Rupert. It was just a fleeting moment that shouldn't have happened," the source also told People. "She never meant to hurt anyone. She's a good person who just made a bad choice."

Stewart, 22, and Pattinson, 26, met while filming Twilight together in 2008. For years they remained incredibly private about their off-screen relationship, but in recent months the pair have been much more open with their affection. In October Kristen told British GQ, "My boyfriend is English" and in May the couple was spotted smooching in Cannes. There was no sign of trouble at the Teen Choice Awards on Sunday night when Rob and Kristen accepted the "Ultimate Choice" award.

So what do you think Robsten fans? Could the rumors be true? Are we about the see the demise of one of Hollywood's hottest young couples? Hit the comments with your thoughts!