The "ballet shoes" the girls wear throughout the film are far too modern for the era depicted.
The evening before Petrova and Pauline's early morning audition, Nana says she can't make new dresses for them, because she has no fabric. Petrova offers to pay for new fabric, and so we see the girls attend the audition in their new dresses. But how did Nana have time to buy the fabric, fit and sew two dresses overnight?