Watch the part where Lindsey's character walks into the gym after winning the debate. They start with a shot from behind her, and you can see that her hands are up in her sleeves. Then, the camera makes a fast cut to a shot in front of her, and her hands are magically out of the sleeves!
First of all, she doesn't win a debate, she won a mathletes competition. That is in no way a debate. Second, her jacket is big, the sleeves are long and wide, and yes, at first, it looks like her arms aren't in the sleeves. I didn't think so at first either, but they are the whole time.