Sorry but that's just .... You have no idea how far this has gone for her. For all you know, she could also be knocking off banks at night and does this for kicks during the day. Point is, when people decide to do something that is blatantly against the law, there is no half measures in my book. As someone else noted, I believe criminals that are caught but not turned in are more likely to think that they can get away with it again rather than being "scared straight".
By the way, jail time isn't the only sentence that comes from this. That's left to the judge to decide and typically revolves the entire facts, including any previous issues. Let the courts handle that part. We've dedicated a lot of time, resources, and effort to make sure this system is in place. How about giving it a chance to work before bypassing it? I'm not sure if this happened in the US, but if it did, please see above.
This whole thought process of the system makes the criminal is ridiculous. It's been proven to be false over and over again but people still believe it's true.
edit: Changed my wording a bit, realized it may have come off as attacks against the poster.