Continuity mistake: In the scene where Lizzie's parents are seeing her off for her trip to Rome, she first walks away from her family after exchanging hugs and the legs of her pants are rolled up. She then turns around and walks back for a second hug with her mother and when she turns around and walks away from the family a second time, her pants are no longer rolled up.
Revealing mistake: Lizzie has black nail polish and the same size of nails throughout the entire movie. Supposedly, Lizzie and Isabella are different people. But, when Isabella comes back, you can see she has the same color nail polish and the same size of nails as Lizzie. I don't think it's just a coincidence.