Editor’s Note: Delving into the archives of pop culture history, “ Remember When? ” is a CNN Style series offering a nostalgic look at the celebrity outfits that defined their eras. CNN  —  She was the most influential style icon of the 1990s. And the Met Gala was, as it is today, fashion’s biggest night out. So, while it may come as a surprise that Princess Diana only attended the annual fundraiser once, in 1996, it’s little wonder she was the center of attention. Then the Princess of Wales,