I will agree with the rest of the critiques that this is a very lovely photo. The lighting is perfect and makes her skin glow and lets her hair color shine. Her skin seems almost flawless. I say almost due to the fact that my eyes went to her elbow and nails. But to be honest my eyes went straight to her chest when I saw this photo. Perhaps it's the fact that her back is arched on the stairs, but her breasts seem to be the main focus. Which I know you didn't mean to do so, but it is. Her dress is very lovely and it would have been better if she was on her stomach and looking towards the camera with a dreamy gaze. I do like the fact that her hands are locked together in a sense, it shows some sort of shield. Her eyebrows seem to be frowning in this angle which creates tensity in the photo.
No matter what, this photo is lovely. Her face is very angelic and the environment is relaxing. You picked a lovely model.