"Stop eating hamburgers," he says, and it's almost sniping, mostly flippant. But he gestures for her to sit down, so it must be fine. To Severus, there are dark creatures, and then there is the fae; the true fae, not the inbred watered-down pets that flit about the edges of the wizarding world, but the horrors that keep to themselves away from the rest of these mere mortals. A genuine elf or fairy could cut him up into tiny charmed pieces with the slightest glance - the fact that this whatever-she-might-be is soliciting his help suggests she could not, in fact, do such a thing, but Severus is not a willful idiot.

(He's also curious.)

"You have nightmares."