Oh, she can tell. She wouldn't be getting a general air of good vibes from him if he weren't. People who've sold their souls, or otherwise disposed of them, have done them for reasons which, in her universe, are really extremely very not good. It's not possible to take someone else's without permission-- meaning they can be freely GIVEN, but not STOLEN. So there's no innocents involved when a true soulless person turns up.

And anyway, they tend to be bigger assholes than Bruce.

"Uh huh. And how's that turning out for you?" She does not comment on the fact that he just joked about being in prison. True or not, she'd really rather not know.