Well, Wallis Simpson was fairly trashy for her time and of course the Queen had nothing to do with that. I think she sympathized with her sister but her advisors forbade the marriage. Of course Margaret could have given up her title, but she wouldn’t. She had a miserable life as it turned out.
As usual, I don't remember much about it except an overall impression. Margaret called her sister Lilibet. They had a very formal and structured upbringing. Overall, it wasn't a life I would have wanted and even less so now.
I guess one doesn't want to try to embed an amazon picture, miles of coding. Found an easier one. This was the exact one. 1940's. Was pretty young when I read it then.