Who is Mrs. Greenstein from Into the Woods and what is their importance?

Mrs. Greenstein is the principal at Grace's new school in Florida. She is described as a small woman, who has dark eyes that scowl more often than not. Greenstein is a reactionary, preferring to deal with the actions at hand rather than the events that caused them. As a result, the only one facing disciplinary action after a brawl in the hallways is Grace, despite the fact that her record of behavior is exemplary, and she had been provoked mercilessly.