Dover was pretty cool, other day trips: Warwick Castle, Cambridge, Oxford
Warwick looks like it has some special stuff during Christmas.
https://www.warwick-castle.com/
we didn't take official tours, just hopped on the train to Cambridge or Warwick. We rented a car for our trip to Dover, gave a little more flexibility, but I understand if you don't want to drive while there.
I would see if she'll reconsider on Bath/Stonehenge. They really are cool.