Maria Grasso beat odds of 76 million-to-1 to scoop the US's second biggest lottery payout - a prize of nearly $200m.
"I couldn't believe it. I haven't had time to think clearly," she said.
Her Big Game jackpot was the world's biggest lottery prize won by a single person.
Financial priorities
Ms Grasso left Chile 28 years ago and has been working in Boston as a nanny to four children. The 54-year-old became a US citizen in 1984.
Ms Grasso said she was not sure what she would do with the money.
But she said her priority now was to help her own two children, and her family, most of who still live in Chile.
![[ image: width=150]](/olmedia/315000/images/_319739_jackpots150.gif)
"She fully deserves what has happened to her," a woman named Ana, who said she was Ms Grasso's sister, told National Television in Chile.
"She has worked hard all her life to help her family, especially our mother," Ana added.
Since finding out on 6 April that she had won, Ms Grasso's only major purchase has been the navy blue suit she wore to the news conference at the Big Game headquarters.
"I'm a very down-to-earth person," she said.
'Deserves a good turn'
Ms Grasso waited until Wednesday to come forward and collect her prize, saying she needed time to get a lawyer and clear her head.
Until she left her babysitting job last week, Ms Grasso worked for the family of Chris Gabrieli, a Boston venture capitalist who ran for Congress last year.
She had been living with the family since 1996.
"She's the kind of person who deserves a good turn in life," said Mr Gabrieli, himself worth $25m-125m.
The largest jackpot in the US was won last July by a group of 13 machinists from Ohio, who claimed a prize of nearly $300m.
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