I was discussing this with my friends, and we all came to the conclusion that she may not look the part now, but she might with a good hair dye, a few less pounds (Katniss is supposed to be skeletal) and make up.
And so since I have some (very vague) skills in photoshopping, I decided to try to get a better idea of what JL would look like as a brunette. So, um. Here:
I removed a strand of hair that was lying on her right cheek, so if it looks like she has facial hair... She actually doesn't (sorry, Jennifer).
I think she already looks a lot more like Katniss than in, say... This picture:
What do you think?