Then people of Lady Susan's generation shouldn't be working at the Palace if they don't understand that making assumptions about where a person was born, based on their skin color, their accent, their manner of dress, etc, is a form of bigotry.

And surely people of all ages should be able to figure out that one does not badger guests by repeatedly asking a question until one is satisfied with the answer. It's rude and has nothing to do with wokeness.

I doubt it was a set-up. Lady Susan initiated the conservation and picked the wrong woman to quiz about her ethnicity. The fact that her victim has shown support for Harry's wife doesn't change the fact that Lady Susan was guilty of rudeness at best, racism at worst.