A big soft light bounced off a white wall (in a white room) vs a direct flash from behind to highlight the hair. Note that there was a small gold reflector to Nicole's right in order to bring back some light on the darker side of her face.
Since this was shot in a smallish white room, even when fully backlighted, there is enough light bouncing around to get some light on Nicole's face.
ALSO, each shot was processed to bring them to roughly equal brightness — otherwise the more backlighted images would be entirely silhouetted. They also get grainier as they go to more backlighting because they were essentially underexposed, and when I brought the brightness up, noise became more prominent.
Bottom Line: Even harsh backlight can produce a dramatic result.