Fourteen year-old Betty Grable (the film was already completed before she celebrated her fifteenth birthday) is easily recognizable as the Bakery Girl who takes the order for the chocolate cake with the pansy on it in the opening sequence, then proceeds to lead the chorus line in the "Bend Down Sister" number.
The American Film Institute Catalog of Feature Films 1931-1940 lists Ruth Etting as one of the Goldwyn Girls, but she does not appear in this film. The AFI apparently confused her with Ruth Eddings, who does appear.