Sarah Larson, ex- girlfriend of George Clooney, is enjoying the Sundance Film Festival over the weekend and no, Larson wasn't invited.

She was partying pretty hard, reportedly, after sneaking in through the back door, provocatively grinding half a dozen men on the dance floor, At the Hard Rock Hotel & Casino, after-party for the film The Vicious Kind.

Sarah was grinding on Ryan Cabrera all night, her legs wrapped around his waist, massaging the small of his back, and was seen sneaking out the door with with Ashlee Simpson's ex Ryan Cabrera., source said .

Sarah Larson is a waitress and reportedly a model and actress. But she is apparently one of those models without portfolio.