#1 The background isn't working for me here. Since she's young she wears the shadows well but I think I'd like to see a little more reflected light on her face.
#2 Pose, expression-especially expression-and cropping are right on the money but she has a lot of hotspots through her hair that detract from her perfectly lit face.
#3 Here the background looks like it belongs. Classic senior portrait but her pose and smile looks forced and I know she has the rest of her left arm because I've seen it in the other pictures.
#4 Is a really nice portrait and brings out what you've captured all along-her wholesome beauty. But I like #3 the best.