That isn't the question she was expecting. Misa freezes for a moment or two, uncertain how to answer.

"Because... I wanted to do anything I could to help everyone get back safe. Nathan is a good kid, and Lazarus... I care about him a lot."

She averts her eyes, a little embarrassed to be saying it out loud, but that's probably where the real answer lies. "I like Lazarus, a lot. And he's done me a lot of favors, so I wanted to do something for him. I couldn't just leave while he was like that."