Revealing mistake: In one shot when Alice is in the shower, as she turns for the soap you can tell she is wearing brown underwear. (00:03:30)
Revealing mistake: When Alice picks up the photocopied sheet about Amanda Kruger, if you pause, and read the article, it is actually about tax and the government. (00:53:30)
Revealing mistake: When Jacob says to Freddy "I wanna learn stuff from you, she's no fun anymore" Freddy then raises his metal claw to his nose. His nose then hits the claw, and it bends. (01:17:05)
Revealing mistake: The fake hand that the wires snake into was shot backwards and reversed, so you can see the holes where the wires are going to enter. (00:26:55)
Revealing mistake: When Alice has a sudden vision of Dan falling to hell (or wherever) behind her, the perspective she has is impossible. The fall-away shot starts from an extreme close-up of Dan such that his head alone is twice the size of Alice, making it obvious that this is nothing but a filmed visual inserted into the background. (00:29:24)
Answer: Her death was from Freddy overfeeding her while in the real world she choked to death.