DAT'S RACIST
I grabbed on to the little sister thing even in the film. That's such a common trope that it didn't have to be explicitly mentioned. I don't think casting had anything to do with it. I actually loved the girl who played Rue. What I disliked was that Rue only had like 3 minutes of screen time. We knew nothing about her as a film audience other than her abilities. All we see is Katniss being sad from losing a friend... a riot over her death... and her partner from District 11 getting revenge.
Unfortunately, Katniss isn't all that likable to begin with, so it doesn't even translate to empathy. We barely ever see her partner on screen other than that scene, so he only serves to kill off the hilarious over-the-top-villain knife chick. The riot is the best the movie can do to make us feel something... and it fails.
You wanna talk about racist? The black dude gets offed by a bunch of dogs of screen. My family laughed out loud.