For me, it needs cropping to a different size ratio to reduce that large out of focus area on the right. Part of the left side could also be reduced, if necessary, to achieve a desired size.
An interesting shot in need of a much tighter crop. The out of focus area on the right side of the image and the white on the left are quite distracting and take away from the overall image. I think your idea to desaturate everything other than "spidergirl" is a good one, otherwise there would be too much "competition" with the subject.
The white shirt on the left still pops out to much. Have you considered dodging it in post to tone it down a bit more?