She shouldn't have done it, one. Two, she should have never told the author that she did, and three he shouldn't have published that part of the account.
Federal sentences are almost entirely in the hands of the judge, except in the case of statutory minimum sentences. While there are Federal Sentencing Guidelines, they are not mandatory, and judges may depart from them in either direction within the range set for each offense.
Heck, even in a federal plea bargain, the parties don't usually (can't, IIRC) include a sentence; they can include an agreement on how to apply the guidelines factor and a joint recommendation to the judge on whether to depart (presumably downward) from the guidelines, but the judge still sets the sentence.