She claimed she mistranslated Lottie because she genuinely thought Lottie was dangerous (I don’t think we know why) and wanted to protect Miyamoto from her. John obviously set things up at the beginning to make her seem like the most likely suspect, which makes her a red herring (unless it turns out it actually WAS her, since we don’t actually know who did it yet- John has been known to subvert tropes at times). At the end of the story, she sure wasn’t acting as if she was the guilty party.