[ That is not a question she is willing to answer this kid in a non-scientific manner, so she mulls over the question until she can think of a proper answer for it. She stares at him for a few seconds during the pause.

With the sensitive Victorian nose that Ciel has, he can probably get that the one thing that smells like a greasy vat of meat... is her. ]

I don't think it really matters. There are probably more important things to worry about. Like what the deal with this Julius Vincere guy is.