I'm still trying to figure out why she would throw away her political career, making almost $90k a year, disgrace her husband who is well-respected, and face jail time for $6k. There has to be more to this story. Maybe this was just a downpayment?
They only needed to prove it happened once. This incident is not an isolated, one time thing. This was the one transaction they could prove with no problems. They didn't get Al Capone for what everyone knew he was doing...murder, running booze...etc, they got him for tax evasion.