Its working in chipotle. Quite possibly the worst fast food place in the states. She should be assigned to work in a prison commissary instead. Much more humane.
Any punishment that isn't a fine, jail time, or community service is unusual by definition because those are the typical consequences. However, it is written into our laws that a judge may deviate from this norm if they feel it more suitable. So yes, a judge could interpret this as unusual, but I they have the legal freedom to decide it's not.
She was also given a choice so she isn't being forced into the "unusual" punishment. She chose it over conventional punishments.
This link does a better job of elaboting than I could. But essentially there are punishments outlined for particular crimes. However, the judge may determine the severity of the outlined punishment on a case by case basis. Also, there are alternative punishments that a judge may use at their discretion, or at the request of the defense.