Meet the new Supergirl. According to Variety, Milly Alcock has been cast as the latest live-action version of DC’s famous superhero. She is expected to debut in the first movie in the new DC Universe, James Gunn’s Superman: Legacy. The character will then spin off into her own solo film, Supergirl: Woman of Tomorrow, supposedly based on a recent comic-book storyline written by Tom King and illustrated by Bilquis Evely. The 23-year-old Alcock, originally from Australia, is best known for her role as the young Rhaenyra Targaryen on the first season of HBO’s Game of Thrones spinoff show, House of…