Kristen Stewart, Robert Pattinson’s Relationship Under Siege as Accusations Of Actress’ Infidelity Surfaces

at 8:55 pm | By

Kristen Stewart is remaining silent on claims that she cheated on boyfriend Robert Pattinson with Snow White and the Huntsman director Rupert Sanders, a married man.

Though her rep has yet to respond to Celebuzz‘s request for comment, PEOPLE is reporting the allegations that she had a “brief fling” with the father of two.

What are sources saying?

“Kristen is absolutely devastated,” one source told the publication, which published the report on its website late on Tuesday night before its chief rival US Weekly, hit newsstands with photos that touted it as putting Stewart, 22, in a compromising position.

“It was a mistake and a complete lapse in judgment.”

The source went on to tell PEOPLE that the fling did not constitute an affair.

“It was just a fleeting moment that shouldn’t have happened,” the source said. “She never meant to hurt anyone. She’s a good person who just made a bad choice.”

A source close to the actress told Gossip Cop, “It’s not a relationship,” adding that Stewart “is not with him.”

A rep for Sanders, who is married and has two children, could not be reached for comment when contacted by PEOPLE.

The reports come on the eve of the much anticipated release of The Twilight Saga: Breaking Dawn Part 2, which hits theaters in November 2012.

Just this week Pattinson, 26,  denied rumors he and Stewart, 22, were marrying:

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