“The Crown,” Netflix’s family drama that views 20th century history through the eyes of Queen Elizabeth II and the royal family, has long grappled with the themes of women, power and duty. When it returns Sunday for its fourth season, the series adds two more complicated women: Margaret Thatcher (Gillian Anderson) becomes Britain’s first female prime minister and a young Lady Diana Spencer (Emma Corrin) becomes the Princess of Wales.
Erin Doherty plays yet another. As Princess Anne, the straight-talking royal is a frequent…