Mary didn't know who he was talking about, but she couldn't help but smile at the fondness in his voice and expression as he described the woman.
She frowned and looked away at the next question. There was a complicated answer to that one, and a slightly simpler one. Neither of them were simple really.
She also wasn't sure how much she should share, though there was just something about this man-or alien, if he could be believed-that inspired an awful lot of trust. She looked back to the Doctor.
"Long story short? We're hunters. We go after the supernatural-ghosts, werewolves, vampires, anything that shouldn't belong in this world but is still out preying on innocents."
And sometimes not-so-innocents, but even if they weren't snow-white, most people didn't deserve to die at the hands of something that shouldn't exist outside of nightmares and horror movies.
"So me saving mom probably will help save the world from this Hellmouth down the road. It's just a matter of when. And now I just need to find my sister so we can get back and let my parents do their job."
If she was meant to help with the Hellmouth or even if she wasn't but was needed, she'd help with that too. She couldn't just turn her back if she was needed for something like that. Especially not with her family and the man she cared about so close to the situation. But she could accept that she might not be meant to help with that. That her part had already been played and now she just needed to save her sister so they could both go home.