Two things: You need a lot of light from the back to cover the shadows. Look at the background, the bed should be centered or the model should sit in the miggle of the bed so you don't have the spare space on the right.
Pick up Photoshop Cosmetic Surgery if you get a chance to also helps with alot of the post processing its by Barry Jackson and the ISBN 978-1-57990-800-3
trust me its worth it.
