A witch's name is not the same as a name with the meaning: witch. presumably a witch could have any name she chose, and if she was a sensible witch she'd choose something mainstream like Amy or Tracy rather than something out of the Addams Family.
As for a name that means: witch, I can't for the life of me imagine why anyone who believed in witchcraft would use one for a child, if such a name exists. If the family are witches, why single out one member? If they aren't, why make a false claim that might attract incendiary attention? And if you don't believe in witchcraft there seems, if anything, even less point.