Kristen Stewart busted cheating on Robert Pattinson?

Reports flooding out of the US suggest that's the case.

People is reporting the starlet cheated with Snow White and the Huntsman director - who's married with two children - Rupert Sanders.

Sanders' wife, who also appeared in Snow White and the Hunstman, posted a one word tweet - "WOW" - earlier today before deleting her account.

"Kristen is absolutely devastated," People quote a 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."

Photo: Getty Images / Getty Images Entertainment / Kevin Winter