Hot rapper Azealia Banks announced on Twitter that she’ll perform at the Costume Institute gala May 7, but she may not have been the first choice. Sources tell us Nicki Minaj had been invited to do the event, but she never signed a contract, leaving organizers Vogue and Prada hanging as late as last week. Banks tweeted yesterday, “I’ve Been invited to Perform for PRADA next week in NYC! Gonna b so lush !! Let’s see what new songs I debut there! #metball2012.” She also tweeted she’s attending with Alexander Wang, who designed her outfit for her Met gig. Both tweets were removed from Banks’ feed by day’s end, perhaps to keep what was left of the surprise. A Vogue rep had no comment.