REGAL ROSES: Bearing flowers, Charles and Camilla visit Hanover Square, where they left a tribute to British 9/11 victims. Photo: AFP/Getty Diana would be amused. Her successor and former rival, Camilla Parker Bowles, failed spectacularly in her attempt to wow Manhattan society with her sartorial splendor last night. Dressed in an unflattering Anthony Price navy velvet frock with a fussy oversized chiffon collar, the Duchess of Cornwall arrived at a chi-chi cocktail party looking more like an escapee from the choirboy pew of Westminister Abbey than the guest of honor. Earlier, Camilla caused quite a stir when she chose...