The dad snooping through the teenagers room (SPOILERS)
It's clear that the movie wants to show the viewers that the dad has the type of relationship with the teenage daughter where he goes through her things and she's completely fine with it, but what teenager is truly okay with their parents going through their personal stuff?!
Maybe they thought they could pull it off due to what happened to the other daughter, and everything the family's been through, maybe him being able to go through her stuff would seem more plausible.