The moment this movie tricked us
When the devil girl sees the real one and she get shocked that 'who the hell is that girl in the car' is the moments the movie tricked us all. As long as you are devil you know who you are and you know your mission.
Okay you may be in an accident and you lose some of your memory but before it you know exactly who you are, so why the hell she was so shocked at the start and in the apartment when he killed the real girl he wasn't shocked anymore and she killed her with that devil like face. I don't say it wasn't guessable that the person we saw the devil itself but i don't like the idea of tricking people into whatever you want just to make the movie more interesting!