[equalunique]

Maybe her friendship with her coworkers motivated her to do her best to leave things in a semi-workable state for the team. It could be that she was uniquely capable in her role, which is why she felt responsible for completing certain work that would lead others to struggle even more. Capability as well as the attitude that accompanies it may explain why her pay doubled at the new job. For several people I know and myself, this seems to be the most prominent reason for staying past the committed time. Twelve hours after closing time is extreme, though.