Mozart music question

I have the original soundtrack based on this movie, there is a duet that appears in Act 1, Scene 5, it's when Clara is watching a mini performance during the dinner party that tells a bit of back story about how the prince became the Nutcracker. It's also where Clara finds the Nutcracker in the Christmas tree. It is a short opera piece, that's included on the soundtrack - track 15, called "Duet of Daphnis & Chloe" from "The Queen of Spades" (La Pique Dame), it says it is played where Clara and Drosselmeyer watch a Pas de Trois. It was an extra piece added to the movie that was written by Tchaikovsky, not Mozart. I do know they used a Mozart bust on top of a bookshelf during Clara dream with the battle of the mice and soldiers. I think they may have confused this, but if I find anything different I'll let you know.