How much do you get for the "Baby Bonus" nowadays? is it $5K? Because at 6 kids she's already pocketed $30 000.00, plus benefits for each child because she'd have a hard time working with 6 small kids at such a young age...
Besides, you need a court order to sterilise someone against their will, and it's hard to get, regardless of the circumstances - I know this for a fact and I've seen what it takes to get it done. No doctor is going to perform that procedure without legal consent. No way no how, even if the person undergoing the procedure is probably going to be incapable of suing.
And damn, 6 kids at 21?! WTF!