Joan, I was trying to get for you a natural light, light/shadow composition equivalent to what Chris Saper achieved in her post "Brown Shawl", linked
here.
She used artificial light in her setup; you may not have a strong enough light source from your window for this, at least at the time of the day that you took the photo. Maybe a different time of the day? Or a different room of the house? Maybe you should move the camera a bit as well as having your model move? How about cutting down all the bushes in front of your house?
Where is Mike McCarty when you need him?
The goal here is not necessarily to find a "formula", stock portrait pose which you will always use; rather, it's to come up with one very successful example of light management which you will therefore 1. succeed at painting a great "form" portrait, 2. feel justifiably self-confident about it, and 3. move on from there.