Not really her fault. We'd been having a long conversation over IM. She then sent a message to me and Carol. She got a response from Carol (indicating that it had been seen) and we carried on talking in the main thread. It was entirely reasonable for her to assume I'd seen it. Should she have followed up with an email? A phone call? Possibly. But she had evidence in writing that she'd asked me to do something. This is 100% Google's fault for not telling her that the message wasn't delivered to me.