Daphne Guinness will get dressed for the Metropolitan Museum of Art Costume Institute Gala in the windows of Barneys as part of an art installation at the famed Madison Avenue store. Style queen Guinness and Barneys are collaborating on a six-week exhibition, “Fashion as Art,” where Guinness will conduct several performances — one of which will be the fashion muse prepping for the gala in full view of shoppers and passersby. The installation will also include items from Guinness’ wardrobe, including pieces acquired from style icon Isabella Blow, and a short documentary on Guinness. The Barneys project launches May 2, the day of the Costume Institute Gala, to celebrate the opening of the exhibit “Alexander McQueen: Savage Beauty.”