Michael Angelo
There's a big difference between a normal White Witch and a Grand White Witch.
Sure, the title would be considered as one. But the most factor that differentiates the two from each other was the power to heal.
Normal White Witches can only heal injuries and cure illnesses, while Grand White Witches can revive a person even after the body was buried and only bone is left.
Not to mention, the power to cause damage.
Grand White Witches do not inflict harm, earning them their extinction. As for a normal White Witch, they could bring death with just a snap of a finger - literally.
Yes, it may sound confusing on the white witch stuff, knowing they also heal people, but it's part of the curse their marks bear; they can't stop it, even if they wanted to...