It's called a plea deal. She helped out the investigation and got other people convicted. She probably would have gotten no sentence at all if the crime hadn't

It's called a plea deal. She helped out the investigation and got other people convicted. She probably would have gotten no sentence at all if the crime hadn't been so bad. The Judge "believed Ms. Ellison was genuinely remorseful and that her cooperation had been substantial." The remorseful bit is a very important component here. She didn't commit the crime with the intention of gaming the system later to get away with it. Personally, I'm okay with this. It's a huge incentive for others involved in a criminal enterprise to do the same thing in the future. It's worth letting one person off lightly to guarantee you get everyone else.