A Marietta woman accused of using her job as a law firm secretary to embezzle more than $830,000 was sentenced to federal prison Friday.

Francine Fonger, 50, who pleaded guilty to one count of mail fraud in August, was given three years and one month in prison, to be followed by three years of supervised release, the U.S. Attorney’s Office in Atlanta announced.

Fonger was a longtime employee at an Atlanta law firm whose name authorities did not disclose.

While working as a legal assistant, she was assigned to help a retired partner at the firm with his personal business, including paying bills and doing bookkeeping. She later started using his money for herself and her bills, prosecutors said. The scheme ended in December 2010, but authorities said it dated back to at least 1999.

“This was an extraordinary long-running fraud by an employee of a respected law firm,” Mark F. Giuliano, special agent in charge of the FBI’s Atlanta office, said in the news release.

Fonger must pay $832,890.35 in restitution to the estate of the now deceased victim.