Sara Mota de Larrea ($11.6 billion)
Source: https://www.laguiadelvaron.com/
This lady is a Mexican billionaire after her husband Jorge died in 1999, the founder of the mining company Grupo Mexico. He was the copper king of Mexico. Sara inherited 32% of the stock of Grupo Mexico when Jorge died. Grupo Mexico has the largest copper reserves in the world. She also runs the largest railroad business and oil-drilling firm in Mexico. Her son German took the reins of the company in 1994. Sara is the biggest shareholder of Empresarios Industriales de Mexico, a holding company in Arizona. It manages Grupo Mexico with 38.5% holding shares.