Crossover success of Vera Wang from celebrity bridal designs to slinky after-dark party fashions is like adding whipped cream to ice cream. She takes shiny fabric, ruffles and poufs of net to emphasize girlish figures and guarantees that her dancing beauties in tart chartreuse and metallic gleam will never be wallflowers. Her latest daytime outfits blend Hawaiian and Japanese flavor with a touch of Western style.