The thing is? She wasn't the girl you knew anymore. The corruption had started to take over her heart and change her. If we didn't purify her...it'd be a little like rotting on the inside. Is that any nicer to her?

[They sound sympathetic at least. ] I'm sorry. I don't know why it chose her. Not really. But we had to save her, and this was the only way to help her and Tsurumaru.

The universe isn't always nice to people who blatantly ignore a problem.