Sienna Miller has laughed off rumours she's dating actor Josh Hartnett. The 25-year-old actress was asked about the rumoured romance as she was snapped touching down in Salt Lake City, Utah, for the Sundance Film Festival. Miller and Hartnett, 28, were spotted getting cozy last week as they sat side-by-side on a couch in Hollywood's Chateau Marmont hotel. But Miller - who was wearing a grey beanie bobble hat to brave the cold - said there was nothing to the reports. "Absolutely not," the actress said of the stories. Miller is at the festival to promote her new movie 'Factory Girl.' In it she plays tragic Edie Sedgwick, who inspired artist Andy Warhol.