Great capture of mood!
I agree with the first reviewer about the proportions and such. Particularly the legs caught my eyes; it seems like the leg that is propped up should be little larger and more prominent than the other leg.
Other than those items, this is a good composition. You have very nice shading, and I really like how you did her hair's shading in particular (it looks very realistic). One thing I must commend you on is that it seems you've got one light source, which many people have an issue with. The shadows appear in the right spots. Good job and good luck with your future work!