Imagine someone with utterly pitch black skin, and everything about them is that same colour. Their eyes, their teeth, their fingernails. It's like a silhouette. That's Emigre. The area around her is just slightly darker than the rest of the room. You can see her.
The whole "you can't see her" thing is because her body reflects NO light. (That's how your eyes see things, you see the light reflecting off them. Like sonar, but with light.) So your eyes are trying to interpret a woman shaped hole in their vision.