Sarah Larson's Sin City Secrets

They say what happens in Vegas, stays in Vegas. But when it comes to George Clooney's girlfriend, former go-go dancer Sarah Larson, evidence of her wild escapades has been spilling out of Sin City like quarters from a slot machine!

"Sarah looks like she totally belongs, walking down the red carpet on George's arm," a source close to her tells Star. "She's even been described as having a successful runway and print modeling career. But until recently, her modeling career consisted mostly of being paid by promoters for clubs, magazines and radio stations to attend special events in sexy outfits and party with her wild girlfriends!

"Sarah is outgoing and fun and loves to drink. She likes to get wasted when she goes out — but hey, that's what Vegas is all about!"

In one risqué set of photos taken in July 2007 — one month after she first met George, 46, at the Palms resort — Sarah, 29, is wearing a short dress and has her legs wrapped around a man holding her up against a wall in the middle of a crowded Vegas nightclub.

The next day, Sarah — who appears to be drunk — is pictured wearing a bikini at a huge, outdoor pool party at the Hard Rock Hotel & Casino, kneeling on all fours with her backside in the air as she licks the cover of a magazine lying on the ground. She's also shown rolling around on the floor as she wrestles a bikini-clad blonde!

"That's our Sarah!" says the source. "She's not shy in the slightest. She loves hamming it up and is never embarrassed. That's the Sarah everyone in Vegas remembers, not the girl dressed in Valentino minding her manners for the cameras with George at the Oscars!"

For lots more on George's girl — including photos of her sexing it up with a Vegas gal pal — pick up the new issue of Star, on sale now.