A Vancouver woman admitted on Monday that she taught her two children to fake mental retardation in order to obtain state benefits on their behalf. Rosie Costello, 46, pleaded guilty to conspiracy to defraud the government and Social Security fraud.

The U.S. District court heard that Costello, 46, collected more than $280,000 in benefits in over 20 years. Costello said she first filed for federal benefits in 1985 when her daughter, Marie, was 4 years old. Thereafter, she filed for her son Peter's benefits in 1987, when he was 8, according to the Washington newspaper The Columbian.

Peter, now in his late twenties, already pleaded guilty to Social Security fraud earlier this month.

The scam was exposed after Peter was caught on a video defending a traffic ticket in a local court. He is scheduled to be sentenced on May 11 and faces from six months to a year in prison if he's convicted.

Rosie Costello is scheduled for sentencing on May 17, while investigators are still looking for her daughter, Marie.