Welcome; looks like you're off to a good start, but there are a few areas for improvement, most notably in the colour. I'm on a pretty old, crappy monitor here at work, but all three of these have a distinct yellow/green colour cast to them, which leads me to believe that your monitor colours are way off. Read the excellent tutorial
here on the topic of white balance.
In the first image, I would like to see it openeed up a little more; it seems a bit too tight on the sides, and I would suggest rotating her head slightly so that we can see both eyes rather than a little bit of the left. In the second she has a great expression, but I would prefer that the shooting position was lower so that you were not looking down on her quite so much.
Be very careful of your cropping. You have chopped off part of a hand and an arm. Cropping limbs is fine, but if you do it, do it boldly, never at/near/through a joint and NEVER bisect a limb laterally (left arm). Also watch your backgrounds; it's a bit messy and distracting.
I'm not fond of the third image; she has a nice expression, but the lack of light/detail in her hair makes it look awkward, and as with #2, the background is rather messy.
Just my $00.02 worth - your mileage may vary.
~John
http://www.cambridgeincolour.com/tutorials/white-balance.htm