It actually is pretty good overall but you're right, the proportions are a bit off. The head is a bit squashed and the waist is a bit thin but those are minor adjustments that can be fixed. Nothing a little more practice can't fix. The forearm is a little bit thicker than the bicep area...another minor fix. Overall, i think it's a pretty good start. Try either redrawing it (using a light table) or fixing the existing drawing.
It almost looks like you were drawing and noticed you had reached the top of the paper and that's why you squashed her head. I've done it so many times it's not even funny.
