Naomi Watts is already taking on the would-be critics of her upcoming biopic “Diana,” focusing on the late Princess of Wales’ affair with Pakistani heart surgeon Hasnat Khan. “So many people are going to pounce on me for not looking enough like her, not being tall enough, not being properly British — and I am actually properly British; I’m also Australian — but all of those negative comments were sort of floating around in the back of my head,” she tells Hamptons magazine of her decision to take the role. “And obviously the sensitivity of it, is it the right thing to do, how would the boys [Princes William and Harry] feel about it. But they’re not boys; they’re men.” She continues, “They are aware that stories will be told about history and them included.” Watts says she “fell in love” with Diana because she was “fighting to be happy . . . I can’t really think of many people who can survive that level of fame. She was trying to get better and she was trying to move beyond those difficult times.”