You need to get more light on the background if you wanted it to go whiter than it is. Perhaps you meant for it to be that way, but if not, more light on the background. The shadows on the background are partly caused by her being too close to it. If you don't want those shadows there, you could light it differently or move her farther away from it.
That "Couture" pose that she did is killing me. That is so bizarre I can't speak, she looks like she is trying to turn herself inside out backwards, I don't know what. Save her from herself the next time she poses in such a convoluted way. It makes her look deformed. That's not your fault, it is hers, but she probably didn't realize how odd it looks.
My next comment is NOT meant to be snarky, so please don't take it that way, I mean it to be constructive. Even models have physical flaws, and as photographers, we are supposed to make them look good anyway. We can use light and shadow to sculpt a face, hide a flaw. We can use angles to perform visual magic. In this case, the model does not have a pleasing nose profile, so be careful to direct her in such a way that you aren't seeing the bump on her nose. You don't notice it on full on shots, only on profile shots. So you should realize, "Ok, that is a perceived flaw (potentially), I know not to shoot this model in full profile."
Also, a camera distorts features because you are trying to take something 3 dimensional and record it in two dimensions. That distortion can be favorable (Baby, the camera loves ya) or UNFAVORABLE, the pretty girl who doesn't photograph well. Be aware of how a camera distorts features and work to play it up if it is good, OR correct it if it is bad. (The light and angle of the last photo makes her face longer than it really is.)
Those things aside, I like the other poses, she is a beautiful girl! I love her expression in Whaddup Girl. Great eyes. I think you did an excellent job of using the bedsheet as a backdrop. It doesn't look like a bedsheet at all, it looks like seamless, so good for you.