Ending

well, in my opinion he does exist, all the first half of the movie is real, probably the trip she took at the party *beep* her brain completely followed by the suicide bomber that made her go into coma, rest of the movie just kept on going with her mind playing tricks on her by the things she heard around her and making up a story about her being Alex, and replacing her place in his and other way around, and at the end she (more like, the viewers) find out that she's the one in coma... a little bit tricky in my opinion but thats what I got from watching the movie, if you have another explaination I'd love to hear that :) p.s. sorry for the late response

I guess the whole movie is some sort of a strange nightmare, a kafkasque dream about the losing of one's identity. If you follow this thread, it is easy to understand the most implausible twist in the end, since dreams don't have a logical explanation.