My mother has a knack of insulting my wife with backhanded comments. For example, when my wife wears a new dress, she'll say something like, "That dress suits you. It makes your boyish figure look more womanly", or if my wife invites my parents over for dinner and cooks, my mother will insist on bringing food, as she'll say that my kids need real food.
I know how much it bugs my wife, but she's been holding it in just for me. So one day when my mother was mouthing off, I stepped in and told her "I love my wife very dearly - I think she looks great, cooks great, and is simply perfect. I would appreciate it if you stop running her down, or trying to change her, because I cannot love her any more than I already do." You should have seen how over the moon my wife was!