First things first. It IS absolutely a very good first attempt. You've got all the concepts and have an idea of what is supposed to happen but as others have pointed out, there are ares that need some improvement to make it a more interesting capture and more flattering to your subject.
The lighting is a little flat, which means there isn't all that much contrast between the highlight (main light) and shadow (fill light) side of the face and body. If this was a child or infant I would say you did the right thing but adults tend to look better when there is at least 1 stop difference between main and fill. For lack of a better word, it's slightly more dramatic.
Your lights are also falling too low on the subject. You can see how well lit the front of her body and ends of her hair are lit by comparison to the face and the way that the loop off the nose is pointing straight off to the side, whereas it should be angled down towards the corner of the mouth as suyenfung pointed out. You should never lose sight of your subject's face and eyes and they are what lacks life and contrast.
You've got pretty good subject isolation but again, more between the subject's body and the background as opposed to her hair and the background. The top of the head should receive more light. That would happen by simply raising your main light and perhaps the position of the fill source or by adding a hair light of some sort. A hair light can be a cheap flash, strobe or a reflector. You can even use some ambient or sunlight to add highlight to the hair, or a piece of white foam core positioned correctly can bring in a beautiful soft hair light on the shadow side of the head and that really opens things up a lot in terms of contrast and subject to background isolation.
I realize you are working on lighting but just in case you want to work on posing as well, one thing to consider is that she has assumed what is considered a more 'masculine' posture by tilting her head that way. If she were to give a slight tilt the other way, and let the head and far shoulder follow the same line it would look more natural. Nothing says you can't break the rules but I think it's good to learn them and work with them before breaking out.
I know that's a lot to take in but I would start there and see what happens. As I originally said, overall, pretty good for your first attempt. Keep working on it and show us your progress.