#1 - Nice. I would like to have been able to see her left hand. Her whole laft arm kinda disappears into her left leg. It's a little distracting to me. That blade of grass sticking up in from of the rear tire is also distracting. Nice job staying out of the reflection though.
#2 & #3 - Don't really do anything for me.
#4 - The best one. This is really nice. I'm going to pick this one apart. This is all my opinion, but this is how I would make it a better image.
Scan the image from top to bottom. Pick out all the flaws you see. For me, the stray hair to her left is distracting. Nothing an easy PS fix wouldn't cure. Sometimes when the wind's blowing you can't keep all the hair where you'd like it.
However, makeup should be the best it can be before you click the shutter. Take a look under her eyes. Those lines add a few years to her and are not flattering. You can save it in PS as well.
I love the pose, and she does it well. Arms are usually an issue, but her's here are not. That's a good sign for her, she has slender arms. However, a bad sign for her is how her skirt folds over at the bottom. Makes it look like she wore baggy pants or someting. Next time, catch that before you shoot. You coulda had her tug at the bottom of the skirt and pull it down a little to flatten it out.
Overall the colors are a little dull to me and I would like to see about 1/3 to 1/2 stop more exposure on this image. That's an easy levels adjustment. I also feel like there's too much blue in this image. It's a little overbearing and I feel like a little blue cast on to her and cooled her skin too much for my taste. Once again, easy PS fix.
The trick is to get it right in camera. Use a target (grey card) to set exposure and WB. Or set your WB to cloudy and you'll warm her up some. I dunno what settings you used to shoot this, but if I were to guess I would say that you put the WB on shady or sunny. I like skin tones a little warmer.
I hope you don't mind, but took the liberty of fixing all of those things in PS to show you what I mean.
The image is a great start and has lots of potential. Most of the things I hit on should really be fixed before you click the shutter. There's lots of promise here.
#4 - Low key on an African American is hard. For me, she is blending too much into the background.