This whole thing is so gorgeous I could look at it for hours, or at least minuts. I am not sure where to start, but I can start with the colors. It looks perfectly clean, without getting boring, if you know what I mean. The light in it gives me a great worm feeling, which I always look for in pictures like this.
Her hair almost looks like the sand/stone/sand and stone, and also the plants behind, makes me think that she's a part of the nature. At the same time does her dress make her less natural-ish, and put her in focus, in a really cool way.
The composition is perfect from my view, it looks like the river flows out of the picture and into my home, which gives me a feeling of being inside of the picture. That's always a good thing (specially if there's a lovely motive), and her right hand, which is closer than the left one, makes it look more dimensional.
Becouse the model sits in a landscape like this and because of her lovely facial expression, she is so very innocent in many ways, but at the same time her red-ish dress almost looks like a symbol of sin, and the fact that so much of her skin shows, amplifies this. Still she ends up looking innocent, because she has no schoes on and because there is no "dirty" kind of look in her face, which is something I really like about the whole thing.
I would really wish that you had a higher resolution, not because the low one makes the picture look less beautiful, but because I like it so much that I would like to see it bigger. He-he.