I agree with the previous comment, I like it. It makes me think about Avatar for some reason, i.e. that this could be an evil (Red) version of the Navi people. The skin, I guess, reminds me of them for some reason. Other than that this is a nice looking demon with a very... exposing... pose ;) Her expression is a mix of bored and I don't really care but there is still strength in it and I like it.
Some critique however. First, her left arm should be leaning against her knee I guess? However, it looks like it's floating in mid air. Her right arm has great contact with the tigh though, looks really good. Second, the dimensions of the tail very a bit too much for my taste. Would have liked to have seen it be thicker closer to the body but I also know how easy it is to not get that correct. Finally, the background is a bit weak compared to her. Perhaps a more artisitc, darker, background would have been better? I do like how the you've put less detail in the bg however to push focus onto the girl.
So, overall I like this, some exuection that could be better (rationale for 3.5/5) but the design of her, shading and color are all good!