Didn't Natasha's dancer come out later? No matter what her purpose is, there is a very good saying: don't let everyone be a ballet, it's easy.
Natasha's expression is not in place when she dances. You can go to see those classic black swan dances. The expressions of the actresses are very nervous. Watch several videos of black swan ballet, compare them and see the gap.
Of course, judging from the muscles of her arms and legs, she has really practiced for a long time, and her upper body movements are ok, which is not easy for non-professionals.