I have a friend like that, too. Like you, I wouldn't go back. We have an iconic diner chain here and I used to go regularly until food quality and service started to decline. When I was pregnant I went several times, though, for a burger/fries and it was "okay."
Another diner, very well- known by locals, has some strange rules and rude staff. Several years ago now, a bunch of us met up there on a very bad snow day when it was deserted everywhere. One person messaged might not make it. So we were a group of 4, I think and got seated. Then the other person showed up after we ordered, I think, and staff refused to seat her with us saying we were at a table for four, not 5. They wouldn't bring a chair over, wouldn't move us and seated our friend alone at the counter which was for single parties. 😂😂😂
The restaurant was empty save a table of two beside us.
After a hugs fuss, and me talking across the restaurant to my friend to make a point, they finally let her sit with us. I think the couple at the table beside us said something, too.
I've never been back. I'm still holding a grudge. It was bizarre and beyond rude. I still don't understand it.
(Looking at you Tomahawk, N Van)