2 questions
1) What happened to the lady at the beginning? Did Diana kill her? If yes, why didn't we see her body? If not, why didn't she? Probably because she didn't have a reason, and only wanted Sophie's husband?
2) How could Diana go from one area to another? Ok, she could move through darkness inside the house, but how did she go to the husband's workplace, and Rebecca's apartment?
I know that no one can really answer these questions, but hey, whatever. :p
Also, how much better it would be if they never showed us her face. Or if the had to show it to us, to be something better than another generic mummified scary face.