Great stuff dude :O - what lense were you using? I'll try to add some constructive ideas - though - I'm not much of a portrait person myself, the only pix I've done of people really are two SGs who never got their sets picked up

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I like this one best. Has a great depth of field. The fence creates an interesting - but not TOO interesting pattern and I feel like the subject is WELL framed. I think it's a fantastic composition. It's soft - but not too soft.

I like the pose on this one - did you coach that? Coach her look? I think that the composition here has a bit to much of the horse in it. It's a little visually confusing to me. I could see eliminating the horse up to her arm/the saddle. Also, the way her leg leaves the frame it makes my mind picture is sticking straight out - which is odd. Perhaps include some of the bend, or past the knee?

I like the composition and angle of this one too - quite a bit. The only thing that strikes me here is that she's a bit washed out. Which, if you've already corrected the levels and are still left with is difficult to fix. Are you using CS3? I can't remember. You can switch the picture to smart adjustments and that helps a bit with contrasting subjects like her in this type of issue. You might also get around it by darkening up the mid tones with the levels histogram.

This one I really like her attitude, the light in her hair, very beautiful! Fantastic DOF!!! I think the only thing I'd do is bring back what you had in the first pic of the span of her body. It looks like she's cut off from the waste down. Where are her legs? Makes her look a bit inhuman. If there was even a trace of her past her waist (thanks to captain spelling nazi) - this would be a REALLY stunning shot in my opinion.
I hope you don't feel like I'm busting your balls, I think you are a better photographer then I - I'm just rattlin off what I'm seein :).