I don't know. In the first scene with the mutants, they refer to her as a midget and in comparison with other people, she's very short. Teenagers are usually almost the same height as adults (though that's mostly with boys, I guess) and even by the standards of your average middle school, Carrie would be short. (I wore high heeled boots throughout middle school - when I stopped wearing them freshman year, everyone was shocked - including myself - that I was actually on the shorter side of average. It was very bizarre.)