Diane von Furstenberg thinks the newly crowned Duchess of Cambridge matters for more than her style. “She is not a style icon,” the designer said of the former Kate Middleton at a screening of “Sarah’s Key” at MoMA on Monday. “She is so much more. She is so sure of who she is, and should never let go of that.” At an Osteria del Circo after-party hosted by Harvey Weinstein, director Gilles Paquet-Brenner huddled with rocker Courtney Love, Christiane Amanpour, Regis Philbin and Rachel Roy.