The woman who blew the whistle on Tom Petters' $3.7 billion Ponzi scheme, even as she was implicated herself, has been sentenced to one year in prison.

Deanna Coleman was sentenced Thursday in U.S. District Court in St. Paul, Minn. for her October 2008 guilty plea on a charge of conspiracy to commit mail fraud.

She had been Petters assistant for more than a decade when she approached federal prosecutors in 2008 and went on to cooperate with their investigation.

Petters is now serving a 50-year sentence for allegedly orchestrating the scheme, but he's appealing.

Prosecutors say Coleman's help was vital to their case and they asked for leniency, but Judge Richard Kyle says the seriousness of Coleman's crimes compelled him to give her a short prison sentence.