It would help if Lumière actually knew what she was looking for in the first place~
*Nods in satisfaction*
By the way, you're not wrong when your character mentions demon-blood, but just to save any future confusion Lumière is still strictly speaking a human being. She doesn't have enough demon-blood to be considered a demon or even a half breed. So assuming miss meow-meow (Lumière is bad with names) can smell Lumière's scent it would still be human, with just an otherworldly quality that can't be easily described. A demon-touched is someone who is being slowly warped by demonic influence or energy...you know...like radiation poisoning. They will never under normal circumstances achieve demon-hood. It would be more accurate to call them 'demonic humans'.