"Right," she says, and watches the other man go, feeling rather sorry for him- and then feeling very, very uncomfortable. It's very quiet, and for a second she just stares at him, trying to reassemble her thoughts.

"How do you know my name?" she inquires, and then realises it sounds a little demanding, and she doesn't want to pick a fight. "It's just that you aren't old enough to have met me at home," she adds quickly, her brain back in action now and cycling through all the people who could have told him- she's been very careful, after all, to use an alias and not mention her name when at all in doubt, and now he knows and- yes, alright, he's Snape, and she knows Snape's story. Why else would she help the older version of him present in Baedal? But regardless of that, Snape in his twenties was a Death Eater- and she has no idea where this version's allegiances lie.

That and he has an unpleasant air and makes her feel like a deer in the headlights, but that's a trait he shares with his older self and so therefore can't actually be counted as 'potentially evil'.