From The Grey House:
Most humans, like Bethany, were unaware of the creatures in the shadows. Natalia felt it best to keep Bethany and other humans unaware of the creatures. She learned herself, at too early an age, that monsters existed. Not all were non-humans like vampires or werewolves, either. Some of the worst monsters she’d met were humans. Still, the human ones could be held in jails, prisons and hospitals. No one could contain a werewolf in jail. Not for long anyway.
That’s where the Slayers came in. They were sent by God to hold back the monsters. Most times, Slayers killed the monsters outright, even if there were humans around. Natalia didn’t agree with that. She felt there was a better way. She found she could approach most vampires if she was careful. Sometimes, she could approach werewolves, but they were trickier. Too close to the full moon, their rage was just under the surface. She rubbed her shoulder as the memory of Charlie’s betrayal came back to her.