Mombi was not exactly a Witch, because the Good Witch who ruled that part of the Land of Oz had forbidden any other Witch to exist in her dominions. So Tip's guardian, however much she might aspire to working magic, realized it was unlawful to be more than a Sorceress, or at most a Wizardess.

Lyman Frank Baum
Another Quote

You Can't Manage Stress Unless You Do These Three Things