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.
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.