That doesn't seem like the case here though. One of the things she was complaining about was participating in new manager training. 21 direct reports isn't that many. Managers have to prioritize their time differently than other jobs.
Ultimately it seems like she had accepted a transfer to a management position to maintain a job instead of being laid off or being transferred to some other sort of job and then realized that she wasn't cut out for management. It's OK to not be cut out for management, most people aren't, but pretending it was anything extreme is ridiculous.