Try to get the model to "connect" with the camera. As it is now, she looks more like she is ignoring the camera (and hence the viewers) in all three photos. I don't mean the model should look into the camera all the time, but when he/she is not, at least there should be some expression/emotion that you're trying to capture.
Pic 1 - Technically, the exposure is good, and the background is pleasing. There is too much headroom above her. The shadow cast by her arm is harsh, and might benefit from a -2ev fill flash. With her pose, it would be better to include her entire wrists instead of chopping them off. I would reposition her to get a completely blue background to get rid of the small patch of green at the bottom, and to have her turn her head slightly towards the camera, probably looking down.
Pic 2 - The model is slightly underexposed when compared to the background, resulting a pale skin tone. Spot metering on her would probably give a better exposure, and if you're already doing so, probably can try +0.5ev compensation. As mentioned earlier, the pose does not work, and it would be better for her to turn her head to look into the camera. Again I find that the headroom is excessive, and the background is unimpressive, being suffered from too many "hot spots". Try shooting from another angle, or using a longer zoom to compress the background.
Pic 3 -The exposure is suffering from the same problem as #2. Head room is ok, and pose wise it might be better if she looks directly into the camera. Background is noisy, and would benefit by shooting her with a longer lens. Her ring and watch are distracting and should be removed.
All in all, its good effort, and the model is attractive. Hope to see more pictures from you.