Thanks for the comments
In answer to several questions on this and similar shots, it is not an overlay or a "negative sandwich", but actually shot in camera. Basic set up is a black background seamless, model, screen made from a piece of black lace hung between two lightstands with clips to keep it unwrinkled, and a softbox or two camera left or right, or left and right, and maybe a boom light. The softboxes are almost equal to the screen plane, but angled more toward the model. You need a very very slight spill onto the front of the screen, but not much. I first attempted this with film and it was hit and miss on the light placement. With digital it is much easier (as I recall this photo is from one of the film scans).