I liked this film but it left me thinking it could have been much better if it wasn't trying so hard to build mystery that was desperately obvious (two Anas) and not much of a payoff in the end.
Some exploration of the pair in the predicament of both knowing of the separation could have been more interesting. The unhinging/paranoia just wasn't believable or very well done.
Yeah, my first thought when she woke up: There are two of them. It was pretty much confirmed by the behaviour of the others. Later, when her mother talked about the password, that's spelling out: There are TWO. The talk about the soul, when she didn't eat and all that: She was the soul (i.e. the light, strongly implied to be the equivalent of a soul), the other "her" was the one without a soul. Memory is just chemistry of the brain, or some such, the movie tells us. I guess the remaining Anna was supposed to still have no soul at the end, in theory equally as not-fully-existing as the "light" Anna.
The movie ended as an anti-materialism statement. Anna has empathy because she is the soul, the other Anna does not, she's a psychopath, because she has no soul. Of course there was a strong rebirth theme as well, with the caterpillar. I guess Anna was a new kind, both did not belong individually, only together. Material (and materialistic) Anna knew, she just manipulated spiritual empathy Anna, because she was too naive because of her inherent goodness due to her being a soul.
The only neat thing they did was that some scenes were flashbacks to earlier Material Anna. It is evident in the first conversation on the phone with her mother - it can only be material anna, because she doesn't give a damned about her memorabilia, just like she couldn't care less about the tape. She obviously knew the password.