Or he was completely nuts and there was not a logical explanation for anything that he did. She couldn't really afford to try to get inside of his head. It was too messy of a place and truthfully, she wished for nothing more than to get through the rest of her life without crossing paths with the animagus again. After meeting him alone in her home in Hogsmeade, she feared that the next time they met, he wouldn't be so calm or so willing to let her leave. She had to be more careful. That included not allowing a known associate of his to drug her into unconsciousness.