What books can I find featuring a female (eccentric, cynical, or spiteful) protagonist that hexes or curses others (or at least imagines/wishes she has the power to)? It need not be the focus of the story.

I can't think of any. I suppose Snow White would qualify. Her wicked stepmother was a nasty piece of work.

Then you might try the Bible. It's got some very resourceful women. Delilah is one who comes to mind -- the most famous barber in history. (Bill Occham and his razor are the second most famous.)

Then there's Salome who remains the world's most celebrated stripper. She didn't use charms and potions to get John the Baptist's head, of course, but there was magic in the way she shed those seven veils.

I guess Jane Eyre is quite good.