That's true: I moved the camera (just the little movement done during re-arming the shutter) to have the "ghost" sharp and the ambient a little blurred. The first time I did it was a mistake, but I found it was... an interesting mistake!
Thanks all!
Reminds me of the work of Duane Michaels, and that's no bad thing. Like John I find the hi-heels out of keeping with the theme of the photo. The other thing that looks so wrong is the models stance, it looks ever so awkward as if she had a bad back and is relieving her pain.