Correct me if I'm wrong, but isn't self-identifying as a witch a relatively recent phenomenon? The people accused of witchcraft and sub-sequentially burned to death and hung through European history were not Wiccan by a modern understanding. For all intents and purposes, wasn't "Witch" in the time of the original Hansel & Gretel a synonym for sorceress?
Etymology of Witch.
"Þe paynyms ... cleped þe iij kyngis
Magos, þat is to seye
wicchis."
It's kind of a kick-ass word. It seems to have perjorated and recovered at least twice, if one accepts the belief that it has roots in the Gothic word meaning "Holy." That would mean the word has changed meaning about like this:
Meaning Priestess, Gothic era => Meaning Magician, usually evil in Old English => Adjectival form meaning Beautiful around 1700 => Evil Again (Salem nonsense) => Meaning a type of modern pagan.
I haven't seen the movie and don't intend to. It made my Terrible Movie Senses twitch during previews. There's an innate absurdity to the idea of Hansel & Gretel as an action movie it that the makers just didn't have the understanding to see. This is the sort of movie I used to invent when making fun of other movies.
And while I'm stirring a bit of trouble to suggest that identifying as a witch is a recent phenomenon, it's been going on more than long enough for the makers of this movie to understand the new meaning of the word. There was really no excuse for this thing to get past the spec script phase.