You touched on something so important here. Namely, "realism". Katniss Evergreen (I have neither watched the movie nor read the book, hence I am talking about something I know nothing of), in all her glory, is a sort of Mary Sue, isn't she? Exactly because she is in fact devoid of any humanity.
Everything you wrote about is correct. When one is taken out of their natural habitat and put in a completely unknown environment (in my country, we say "The pig was placed where it did not belong" to describe erratic behavior ensuing from a change of habitat; it is actually a rude way of saying people with little self-control given too much power for the wellbeing of the planet and acting on a power trip), there should be a sort of shock, a sort of adaptation period that is characterized by erratic behavior. She should have eaten herself to death had she been hungry for a long period of her life (I think that is what happened), she should have been fascinated with inner plumbing if it were the first time she saw it.
However, the author never thought of such details (but you did, excellent job) because Katniss was not real. She was a perfect (stupid, false little dilemmas do not make a character real; its behavior in non-flabbergasting, ordinary situations is what makes it real) projection of the author's view of herself. And I can just list such novels, one after the other. Think "Twilight", think "50 Shades of Grey".
But where the movie could camouflage all that shallowness was the fact that a movie is a third-person limited POV, even if you get Morgan Freeman to do the narration!!! Shawshank was told by Morgan Freeman (who happened to be a character in the movie, but you know Morgan Freeman never plays a character, the characters always play him) and yet, it still was a third-person limited. Though Katniss might have a resting b-face, maybe inside she is going insane but cannot express it through facial expressions because she is emotionally stunted. That is what you tell yourself.