I think your exposure needs some work. You've done a good job of ensuring that the faces are reasonably exposed despite the bright, overcast sky, but at the expense of the whites in the image. Using a fill light to balance against ambient would have really helped these images. Some animation in her expression would help too.
#4 is the best (IMHO) as her expression fits the pose. The others have potential pose and composition wise (last one needs to be leveled - the slight tilt looks accidental) but to echo Tirediron, the exposure is off. Model's poses are fine but I agree that she needs more facial expression. She's a VERY pretty young lady and I love her outfit choice, if you can get her to relax and show some appropriate expression you'll have a model who will knock peoples socks off.