I felt that the composition was a strong "L-shape" with a circular movement. I posted this at Wet Canvas and am hoping Larry pops in and shares his view of the composition. There are strong diagonals with the line of her dress, the angle of her extended arm. The extended arm, with its underlying darks, helps to give balance to the leaning figure.
Next I did an ink sketch of just the darks then a value study in graphite. In the value study, her face needs to be shaded lightly as the white of her dress is the lightest light. I've found this exercise to be an eye opener for me and plan to do more using the Old Masters works as well as current Masters and studying my own paintings. Hopefully this will lead to better planning and understanding of how to create a memorable painting. .