I'll address each image in a moment, but they all have way too much contrast. There's no detail in the blacks or whites. Overall, I'd say you need to get your lighting under control. An excellent way to reduce contrast is by using reflectors to redirect light into the shadow areas and open (lighten) them up. I'm guessing the lighting here is a combination of natural light and on-camera flash. Use reflectors to bounce some of that natural light back onto your subject.
Image 1
The composition doesn't flatter her. All I really see here is hair and a face. From images #2 & #3 it's obvious that she's thin with a small waist and nice hips. I see none of that in image #1. The pose doesn't due justice to her figure. Also, you've cut off her right hand. You shouldn't normally crop an appendage at a joint, as you have here with her wrist. Also, this image looks a little soft in the face. I don't know what the original looks like, but you may want to apply a little un-sharp mask in Photoshop after you resize your image for display.
Image 2
The best image of the bunch, and easily your best composition. This photograph almost looks like it was made by a different photographer. Good facial expression and good use of depth-of-field. The one thing that bothers me about it is the configuration of her right arm and hand. It looks uncomfortable and a little un-natural. Try to avoid presenting the flat of the hand (either the front or the back) to the camera, as it makes the hand look too large. Try to position women's hands so that you catch the edge, or at least some of the edge.
Image 3
Composition, pose, and lighting are weak here. She's dead-center in the frame. My eye has no incentive to explore the frame. It appears that she's missing her right arm. Her left arm, especially her upper arm, looks too big because it's presented square to the camera. Bring her elbows back towards her body to help eliminate this condition. In general, she's too square to the camera. This young lady has wonderful curves - turn her and make those curves flow through the frame. You've also clipped her fingers again.
The shadows are all over the place here. It looks like you have primary light sources coming from image left (rear), image right (front), and directly in front. I hate to say this, but lighting-wise this is a mess; it doesn't flatter her or her garment. I think your contrast issues are particularly noticible in this image. The color balance also looks off to me in this image, she looks a little green.
Executive summary: Image #2 is nice but has contrast and minor composition issues. Images #1 and #3 need to go back to the drawing board. I hope I didn't come across as mean. Harsh maybe, but not mean.
-Chip "Simon Cowell" Bulgin