If Miss Disney Princess hadn't already proved herself to be a rude, disrespectful and arrogant
witch many times, perhaps she could have been excused as thinking that it was okay to "sass grandma".
However, it must have been drilled into her before and after the engagement/Spectacle, and the BRF growing up that their mother/grandmother primarily held that role at home. At all times she was the monarch - the head of state for many countries, the apex figure of their governments, the custodian of their legacy, and an emblem basically.
It wasn't okay to "sass" her, especially after she'd passed.
This is one of the reasons I can't believe that Sparry is a victim of Smegs. As thick (and high) as he was, he had been taught better.
Perhaps Charles thinks bringing those two back would win him the Nobel Peace Prize. He'd be better off and more useful figuring out how to restore peace in the Middle East