Judges can’t sentence anyone to work at a fast food restaurant. They can however make a deal with the defendant to do almost whatever they want, in lieu of the full sentence they would otherwise face.

Which means if the person doesn’t complete their end of the deal, to the judges satisfaction, the full sentence would be applied.

So she has to do the job, well enough that the manager doesn’t complain to the judge, or else she probably faces a few more months jail time on top of probation.