Not bad for a start...
But I'll be honest in my opinion. I think you should continue to practice and take portraits.
Like what has already been said, there is a hint of sadness, anger, and depression that I sense from your models face.
For the first shot, there is a big distraction right behind the models head. The tree branch looking thing isn't a great thing to have. Remember to always look around your model and remember to examine every portion of the frame. Don't let any distracting elements harm your images composition. The branch as well as the steel pole kind-of take away from your composition. Also, her hair is a bit overexposed at certain areas. I would recommend that you take some sort of black cloth to take away from the natural light hitting your subject as you take the shot. Also, remember to meter the most important part of the frame.. The subject. So for instances like these, I recommend using spot or center-weighted metering modes. I would've also liked to see her sit of straight more than the "bent-neck" "slouch"...
Number 2, Okay not too bad. But there is a bit too much of unimportance. In other words, Perhaps a more close-up and tight frame around the face of your subject, with the background. Just try different poses. Her face is at a somewhat 2/3 pose. Not bad, but perhaps a bit more of her left eye. See her nose? The tip of her nose should not exceed nor lie on the cheek line. It should be just before the cheek line... Either that, or a profile view of only one side of her face. Also, it might have looked a little better if her left hand was not cut by the tree, and then seen again on the other side. Maybe it would have been better if her left hand had a different pose, lying on the tree.
Number 3, Her left eye is cut off except for a tiny bit which I don't really think is very nice. In general, the pose and composition isn't exactly... "good". It's just a bit too distracting. The tree takes away from your models face. A possible shot would've been something like your model being framed by the two tree branches... In the center. It also doesn't seem like she is exactly in focus. Looks like you focused on the tree. I see what you were trying to do, but I think it would've been better using a smaller aperture, and focusing on your model.
All in all, just keep practicing and keep trying new poses, angles, and perspectives. The fact that you are doing this is great. Just keep it up!