“MY GRANDMOTHER, BECOMING QUEEN at a very young age in the days when it was a man’s world, it was very difficult for her to make a difference,” Prince William once noted. In some ways he was right, of course. For female role models, Elizabeth II, who ascended the throne at age 25, could look only to Queen Victoria, who had died a half century prior. And, naturally, she faced challenges that male monarchs had not, including giving birth to two of her four children early in her reign. But despite that, what a difference Elizabeth made in her record 70 years on the throne, during which 15 British prime ministers served at Her Majesty’s pleasure, 13 sitting American Presidents received an audience, and at least 14 generations of corgis…