Vera Ellen in White Christmas stills. Costumes are by Edith Head for the "Minstrel Show/ Mandy" song in the middle of the movie.
Vera Ellen was severely anorexic during the filming of this movie. All of her costumes have a high neckline to hide the fact that she was aging prematurely because of her condition.
UPDATE: For an up close and personal look at this one and only gorgeous dance costume- see the later post Vera Ellen in Detail.