So... (Spoilers)

I've watched the film three times now, and I still can't figure out the whole "faked death" thing. I keep assuming that the death was at least temporarily "real," because of the scene where she's floating in the water. Was there some sort of chemical that she consumed to put her body into a temporary sort of stasis that looks like death? Or did she really die? Because at the end it shows that bit where he puts something in her mouth to "revive" her, and then it showed that scene where her soul came from the mirror. What I took from that is that he preserved a part of her soul and put it back into her when she "died." Would I be correct in this assumption, or was it just a chemical play?