Other mistake: When Alice asks Dan to make her some tea (after he tells her about him and Anna), he walks into the kitchen for just a moment, and comes back to find her gone. He also doesn't see her as he runs downstairs and looks outside. She couldn't have quietly gone down the stairs and out of the building in the short moment that Dan was in the kitchen. If she had moved quickly, there should have been a lot noise from her footsteps.
Factual error: When Julia Roberts takes a photo of Natalie Portman crying she uses a 35mm camera. The final photo in the gallery is from a Hasselblad type camera shooting a square format. All the prints show the full negative and the outside area of the negative. Also when she uses the 35mm camera sometimes she advances the film manually and sometimes you hear a motor drive. It would be either one or the other. Last she doesn't focus the lens when she takes a picture.