Aye to what they said about the torso... looks like the section between her breasts and bellybutton that's the problem. Though I'd have to see the reference to be sure.
Still a very nice pic, love the way you drew her clothes, especially the shirt...
...er, like Pij said.
...so I'm just repeating other people again. Never mind.
It almost looks like her torso is too long but I think it's mostly an illusion created by her low hanging pants and the framing. Although there's not a whole lot of her costume here, I really, really like the job you did on the clothes particularly the folds in her shirt. Well done!