Edinburgh is totally worth it. Went there in the fall of 2018. Beer is expensive, but all the art museums are free. At the castle (not free), she can see where Mary, Queen of Scots, gave birth to James (future king of England), and then she can go to the lower town to visit the church where Agatha Christie got married. She can also visit Holyroodhouse, official Scottish residence of the UK royals.
Highly recommend staying at the Radisson Blu, a hop, skip and a bagpipe from the castle.
And haggis is a "well tidy scran". (don't worry, that means "tasty")