Deliberate mistake: In the scene where we see Bella in her room looking out the window, the months are passing, but she is always wearing the same clothes. (00:28:30)
Deliberate mistake: When Janine smashes the mirror she takes it directly off the wall and raises it above her head, and the reflective side would be facing behind her. The camera immediately cuts to a front view as she's throwing it down and the reflective side is in front. This was probably done for dramatic effect so that the reflective side would hit the ground first.