But why ....**** ultimate spoiler ****
Please don't read this question if you don't wish to ruin the movie for yourself.
My question is, and it's sort of in line with what Jen asked: why should/would the girl have killed her father in the first place?
Wasn't it obvious that he would be arrested for the mom's death? And that he probably would go away for at least a while, if not a very long time?