It was a reward for cooperating with the Feds.
This is done all the time. Have you heard of the name "Sammy the Bull" Gravano? The guy is free today and he apparently murdered dozens of men, even has his own podcast.
Hell he is allowed to work and make money in the U.S while I cannot in Canada! Go and figure that out comrade.
The bottom is that the Feds always give deals, breaks, are more lenient and willing to bend a bit if they receive some assistance from a person. Whether its to solve a crime or fill in the blanks, provide information.
I'm not saying it's always right and this woman should probably be forced to server her full sentence, with the usual parole for good behaviour of what have you. She disgusts me.
That doesn't preclude her being given similar benefits other informants and such have been given. It's the way it works, you know this as well as I do.