Dear Beth,
This is the strongest work I have seen of yours so far! You have done an excellent job on the likeness, and I like the color harmony a great deal.
As to your question at hand, I can only say that every time I have left the background until the end, I have regretted it, because it is very difficult (not impossible, just difficult) to make anything work that is different in either value or temperature work, since you have placed every other stroke in comparison to the background. If this were my painting, I would probably leave the background as is, and integrate the edges of the figure a little more with the background by losing some edges, and softening others...the hair would be a very good place to do this.
I would also look at "disappearing" some of the edges and contrast below the waist. The composition cuts off the hands and leg in an abrupt way, so I would minimize the dark values in the pants, and mat carefully to avoid the tangent where the leg on our left touches the arm on our left.
Only a tiny amount of her face is actually in the light. It looks lilac there are shadows on the face, cast by the hair, with fairly crisp edges near the casting strands. This would be a fun place to really work with shadow edges, because in places like this they can really define form.
Linda is right on the forehead. One of the best discussions on children's facial proportion is in Roberta Carter Clark's
"Painting Vibrant Children's Portraits." If you haven't seen this book, you would probably really enjoy it.
With regard to color temperature, since your light source is cool, make the shadows relatively warmer. They don't need to be hot, only just warm enough that they are differentiated from the color in light. In your photo, the shirt folds in shadow look really blue. I learned from my photographer friend that the reason they appear this way is because the film is sensitive to UV light that our eyes cannot see and the bleach used to make fabric white shows up in the UV range. (That's why they used to call bleach "bluing.") So I think the shirt would read more true to the eye if you let the turning edges stay cool, and very (VERY) slightly warmed the deep folds.
Very nice job.