Ann Kirsten Kennis

That's because on Wednesday, the blond, Polo-wearing woman on the cover of the album her name is Ann Kirsten Kennis, btw filed a lawsuit in Los Angeles Superior Court, claiming the band (or, as they're referred to in the suit, "Vampire Weekend, Inc") and photographer Tod Brody used her image without her permission...

Source: http://www.mtv.com/news/articles/1643796/20100715/vampire_weekend.jhtml