wait, what??? (SPOILERS!!)

There are SOME things in this movie that either didn't make sense, or I missed a whole lot of scenes because it was so dark.
First, nobody seemed at all scared by the ghostly happenings...I'd have left the house on the second day.
Second, When the wife sees these visions (shower scene, etc.) is she seeing them, or dreaming...because they all disappear later, as if they were never there. Which brings me to ...
Third... at the end, when she sees her friend in the bathroom..is she there, or another vision soon to disappear..like it was a distraction to lead her to the wall?
Fourth, At the end, when she is standing outside, why is the wall suddenly pristine again..was this all in her head, because her memory of what happened, and her guilt at its consequences drove her to believe she was now possessed, or was she actually possessed? In which case, is her friend really dead, and won't someone find out very quickly when they go to sell the house?

What did her husband find out that made him tell her to get out of the house right away?! It seems cheesy that we were supposed to surmise all of the answers from that one smirk she gave the camera as they were driving away. And why would the ghost attack the friend in the first place?! What HAPPENED?!?!