A former employee of the Clyde’s restaurant company admitted Wednesday in federal court that she stole more than $600,000 fromthe popular chain over a 10-year span.

Nancy Preston, 55, of Vienna, pleaded guilty in the District’s federal court to mail fraud and faces up to 20 years in prison at her sentencing, which is scheduled for Dec. 12.

Preston was Clyde’s corporate controller from 1992 through 2011 and oversaw the restaurant chain’s budget and accounts. Starting in 2001, she began embezzling money by diverting Clyde’s funds to pay her personal credit card and other personal expenses, federal prosecutors said.