Arundel Castle is one of the oldest and most magnificent castles in England that does not belong to the royal family. The immediate town is called "Arundel", but there is a map if you want to use a bigger city.

How about Newcastle dear girl?
She could be crowned 'Queen of the Geordies'
Perhaps a fountain of Newcastle Brown Ale would be most apposite in the circumstances.

May I be as bold to suggest moving to Switzerland! To the Piz Gloria on the Schilthorn near Mürren in the Bernese Oberland. I had a lovely time there once!

What about Scotland? Eilean Donan Castle, the most romantic castle in the world.

Stirling Castle.Although in Scotland,it is just a few hours by train from London..
It is very much intact,unlike some more famous castles.
At dawn,the supposed ghost of Mary Queen of Scots
walks the halls,
Although she was executed at Fotheringhay Castle,which is now only a mound of stone,after returning from being Queen of France then fleeing to England,Stirling was her favourite.

Orlando in the Golden State of Florida, we have a lovely castle for a Princess!