She always seemed very fond of him as he grew up, and before the Markle fiend came along, they seemed to enjoy one another.
Also she was very hurt by what they did to her and her family. I don’t think that was just concern for appearances.
But...worse than that...she treated poor William like a husband/boyfriend/lover/girlfriend, when she was with the boys, WHICH WAS VERY RARE, by telling him all of her woes, hurt feelings, GOD only knows what else. SHE WAS A LOUSY WIFE AND A LOUSY MOTHER! But typical; read the book about her ancestress, Lady Georgiana, the Duchess of Devonshire.