Lady in the Tower

First: I'm no professional artist, these are just my hobbyist's 2ct. Second: this is my first critique, I hope you find it useful. I try not to be destructive.

Light: In my opinion, the light is too strong (if you look at the clouds, they are not as brightly lit as the arm or face, and the 'blue' arm in the shadows points out 'over-lighting'). The color is fine, but I think you need another shadow color (look at the color of the shadow on the clouds and on her cheek).

Colors: I like them, the blue-yellow contrast of tower frames her well. Perhaps turn her head an edge more, so that the hair also frames her hair and seperates it from the bright sky. In the same way, you could take care that the sky background seperates her hair from the dark window frame.

DOF: slightly too much for my taste, especially at the left two arrows, which seem much more blurry than the ones on the right side - irritating, because the eye catches them as on nearly the same depth level.

Overall: the technique is fine, but the image carries no 'mood' or 'story' over to me. Why is she there? Is she sad (lover leaving?)? Is she plotting something? Watching somebody enviously? Why is her arm held like that? Did she wave somebody goodbye?
The problem is her relatively vague facial expression. Any wrinkles or movement shadows are wiped away by the overlighting; the light leaves only the contour of the face and a hint of the nose. Then, her arm seems to be pointlessly held up. If she carried someting, a whole new story could be told, even with the nearly blank face. If she was holding opera glasses, for example, you could sense her wrath, having perhaps just watched her lover cheating on her. If she held a wine glass, an air of arrogance would support her position high above the ground. Perhaps she has plotted something wicked, and just seen it come to her preferred ending. A slight smile on one mouth corner and one slightly lifted eyebrow would strongly support this interpretation.

So: I think your technique is fine, now you should concentrate on the meaning / content / substance of the image.