That Witch Which

This is the story book / series that Tenley Tych is a big fan of. It's an offbeat fantasy comedy that has also been adapted into an anime. It's later revealed that the lead character's name is Claris, but she's usually referred to as just 'The Witch' because in her world she's the last one.

https://www.amazon.com/dp/B0CFK6M4CB