By Kat Giantis
What does it sound like when a Twi-Hard's heart breaks? A collective cry of "Bella and Edward, nooooooo!" went up on Tuesday afternoon amid accusations that Kristen Stewart two-timed boyfriend Robert Pattinson.
"Kristen is absolutely devastated," a source tells People. "It was a mistake and a complete lapse in judgment."
According to Us, it has photographic evidence of K.Stew's "marathon make out session" on July 17 with Sanders, who has two children with model Liberty Ross.
"It seemed like they couldn't get enough," marveled one paparazzo.
But the People spy insists the alleged dalliance represents nothing more than a short-lived bit of recklessness.
"She wasn't having an affair with Rupert. It was just a fleeting moment that shouldn't have happened," explains the insider. "She never meant to hurt anyone. She's a good person who just made a bad choice."
Neither Stewart, Sanders nor Pattinson has commented.
Earlier this month, the rumor mill had Kristen and Rob on the track to domestic bliss, complete with engagement ring shopping and baby plans.
The "Twilight" twosome, who have been dating for three or so years, were last seen together at Sunday's Teen Choice Awards. They are currently gearing up for the massive "Breaking Dawn -- Part 2" promotional campaign, which just got exponentially more interesting.
Click on to see them at the TCAs, along with plenty more pics …
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