I would say the image over all is a little too dark. If her silhouette were set against a brighter and/or more colorful background it would be more interesting.
I think the only reason I like it is because of the light outlining her face and hair.
But the background (school across the street) sucks for the most part. Was just one of those moments where we took the kids for a walk, I turned and took a picture (with the intent of a silhouette), and this was the end result.
I'm sure she is beautiful. But, for me, the photo flops. Annoying background. Whole thing just dark, not sharp, dramatic silhouette.
You have a great model, keep shooting.