While she has money in many industries, her primary source of wealth is mining. Her net worth is well over 20 billion dollars and some believe that her worth is close to 100 billion dollars which would put her ahead of Carlos Slim and Bill Gates and make her the richest person in the world.
It is always sad when families do not get along. The three eldest children obviously have made a decision that they want some money now, rather than waiting until their mother wants them to have it. In so doing, they are probably foregoing a lot of money down the road because it is very possible that their mother will not provide for them in her own estate planning. On the other hand, maybe they are fairly certain that their mother was unlikely to leave them much.