CTM representatives say their unions defend worker rights, offer perks such as scholarships and sports programs and abide by Mexico's new labor rules.
Along with La Liga, other new unions have also won victories over powerful rivals in the past year at GM, Japan's Panasonic (6752.T) and French glassmaker Saint-Gobain (SGOB.PA), pledging better pay.
Even among the new crop, La Liga stands out for its broader vision: targeting companies no matter the sector, no matter the location.
Leaving her three kids at home, she is traveling factory to factory seeking support.
What's more, to drum up support, La Liga must fight a deeply embedded culture of fear and apathy around speaking out.