'kay, here's my guess as to who sophie and gracie are...
before the show started, my bf and i were hanging out outside of the pavilion seating area.  there were two little girls, maybe ages 6 and 8, dressed in black dresses, makeup, glitter on their faces, and wrapped in glittery gold shawls having their picture taken by a professional photographer.  the girls reminded me of miniature Stevie Nickses.  *lol*  anyway, when v dedicated the song to sophie and gracie, i just assumed she meant those two little girls i had seen.  i don't know why or who they were, but they were obviously getting special treatment.  but that's just my guess *shrug*