oldbaldyone

Answer: Cobb placed a thought in her head that her world isn't real. He intended for this thought to be applied to the limbo world they created, but instead it was applied to the real world. She simply cannot get the idea out of her head that she is still dreaming when in reality, she is awake. Nothing Cobb can say or do can convince her she is wrong, because the one safeguard they have (totems) has been broken because Cobb knows how it works. She simply thinks Cobb is the one with the problem, can't or refuses to wake up, and thinks Cobb is manipulating her totem to make her think she is awake when she is not. We never actually find out if she was wrong or right either :).

oldbaldyone

Answer: In order for a totem to work a person has to be 100% sure it wasn't manipulated by anyone else. If someone else knew what made the totem special you could never be completely sure someone else wasn't manipulating it. The spinning top itself is a bad choice for a totem anyway, since anyone who sees it being used should instantly tell what makes it special. Think about it like this: if you had to keep valuable information locked away in a safe and had to be sure that nobody could ever sneak into the safe, even someone you know and love, you would want a secure combination for that safe that nobody else could guess. If your combination was your birthday, how could you ever be 100% sure that nobody would ever guess the combination? Could you ever be 100% certain that nobody has looked in the safe?

BaconIsMyBFF