Well I dont quite see that it was her idea that the boys shoul go to boarding school.. most royals had done so in the previous generation so why not Will and Harry? I think she got her way about what school they went to, she favoured Eton and Charles having not enjoyed Gordonstoun was willing to back her on that. But yes any family would be angry to find that their problems had been splashed all over the papers and a book had been written to publicise their troubles. Even if they disapproved of C's affair, they weren't going to like di's putting it out there publicly, NOT mentioning her own lovers and into the bargaining hinting that she hoped charles woudld not become king.