Don't expect a clone of Audrey Hepburn in this downtown update of Breakfast at Tiffany's. Parker Posey doesn't do imitations. She's an original -- smart, sexy and the scrappy comic force behind this playfully hip concoction from first-time director Daisy von Scherler Mayer, who co-wrote the script with Harry Birckmayer. Posey has been making herself known on the periphery -- a soap stint on As the World Turns, a sly supporting turn as Darla the school despot in Dazed and Confused. Now the…