Answer for everyone who didn't get it.....

well i saw almost all the threads,and reading people's interpretations about the story.everyone is saying different by different assumptions that this could be the case and that could be the case.but i guess none of you tried to go more deeper into this dilemma.let me take you.

i am a keen observer and i try to search for things i find fishy or questionable.in the film the doctor said,that this is rare kind of syndrome that is called "Folie a deux" (Google for it).but in case the info page is:

http://en.wikipedia.org/wiki/Folie_%C3%A0_deux

this is a syndrome in which one person becomes the dominant one and imposes the thinking on other.but in my view what might have been the answer to story line,is that,father had the syndrome and it transferred to her daughter via genes,and this started same (or somehow changed) revelations in her and she started facing it too.

this might not be the actual reason,but it could be the one of possible ones.