No one imagines that a Christmas rom-com can be renegade. And yet “Happiest Season,” about a couple played by Kristen Stewart and Mackenzie Davis, manages to be at once deeply, warmingly conventional and surprisingly radical, simply by focusing on a pair of women. “I just wanted it to feel very, very relatable — but then also completely new,” said Clea DuVall, the director and co-writer with Mary Holland, who also stars as a loopy sister.
DuVall, who is an actress too (“Veep”), has said her own role in the seminal 2000 comedy “But I’m a Cheerleader,” in which she played a gay teenager sent to conversion camp, helped her out of the closet.