Despite the fact that she had had no idea about the things that Jasnah had spoken about when Jasnah also similarly has no idea what Vanessa speaks of it throws her a little. Others that she'd mentioned magic to had not believed that it existed but they had at least been aware of it. There's a momentary silence where Vanessa decides how exactly to begin.

"Lucifer is the devil. A fallen angel." Though that likely means nothing still. "Witches who worship him use their magic for harm -- for evil." Essentially. Vanessa had used her magic to hurt someone once, taking a life in vengeance of her friend, and it had been a dark moment. She could never take that back, and though Vanessa had still fought against Lucifer it had taken her one footstep closer to him.

"Some witches are born with their power, others learn it." Or are given it from Lucifer.