A time travel book. Or is it a haunting?

Minty believes she is a witch - not the type you would notice ordinarily - - she appears to be like anyone else but is quite used to seeing phantoms floating about the place, and thinks it is perfectly normal. Minty is very determined as well, which is just as important because when she goes to stay with her aunt in the village of Belton she soon realizes that she has a task to do. . .