"They really don't see it as a problem, they just think they've exercised bad judgment," said Shaffer. "They don't see how insidiously it's invaded their life."
O'Connor's annual gambling winnings peaked at $200 million, according to Phillip Halpern, an assistant U.S. attorney. But when O'Connor began to lose, she liquidated her savings, borrowed money from friends and sold real estate, according to prosecutors.
In 2010, she sold her La Jolla, Calif., home, which is down the street from Mitt Romney's, for a reported $2.5 million.
While O'Connor once had a fortune estimated at between $40 million and $50 million, which she inherited from her late husband, she now is nearly broke and living with her sister.
In 2009-2010, O'Connor was estimated to have won more than $1 billion, according to casino documents filed with the Internal Revenue Service. But Iredale said her net losses topped $13 million.
O'Connor, who walked into the courthouse with a cane, did not take questions but apologized for her actions.
"I think most of you that know me here would know that I never meant to hurt the city that I loved," O'Connor said.
The Associated Press contributed to this story.