Canadians don't need a visa to travel to Mexico though [1], assuming they won't be doing any work or studying. Going to the airport to go back to Canada is not work.
She gambled on trying to to game the immigration system and lost. It sucks but 12 days in custody isn't world ending. The most amazing part to me is people with no experience with "the system" find themselves incarcerated and think not eating sounds like a good idea.