Painters think in brushstrokes. Directors think in scenes. Women under 30 think in Instagram stories. Young women’s travel, clothing, hobbies, and even their romantic relationships are subconsciously selected based on what would look best photographed, filtered, and ironically captioned. Digital life and real life are not in competition; they’ve melded. Social media isn’t a hobby or a distraction for young women; it is their medium of self-creation and, in some instances, self-destruction—and it has ruined girlhood, Freya India writes in her debut book GIRLS®: Generation Z and the Commodification of Everything. India, herself a 20-something, surveys the online activity of...