Revealing mistake: When Lizzie awakens on the morning that Edith gets released, Edith doesn't respond and Lizzie goes to her bed to "mourn" the passing of her friend. Except that Edith is still breathing.
Deliberate mistake: Probably best for filming the scene, but Jennifer Hart pulls up and parks her car on the street on a red curb in front of an ambulance and walks away. (00:10:12)