With Your Sister’s Sister, writer-director Lynn Shelton positions herself as an auteur of particularly tricky terrain. She structures her scripts as if they’re challenges to herself, writing the story into tight corners and seeing if she can plausibly extricate the characters. It’s a little like she’s the creator of a television series that specializes in crazy cliffhangers, but instead of meth empires or bipolar spies, Shelton’s territory is far more treacherous: human emotions. As opposed to the earlier Humpday, which found comic drama in the trap of escalating bravado among two friends, both heterosexual, who commit to making a gay porno together, My Sister’s Sister focuses on the trickiness of love, both romantic and familial. Shelton’s script, built collaboratively with the actors (they’re credited as “creative consultants”) focuses on a highly unlikely love triangle. The resulting work is thoughtful and relentlessly exploratory, obviously a gift to its actors, and they give back with impassioned, emotive work, with Emily Blunt and Rosemarie DeWitt turns as loving, surprisingly conflicted siblings running neck-and-neck in the race for the film’s best performance. Fans of Humpday may have been expected something equally provocative, and Your Sister’s Sister was met with some disappointment by those who felt it was a tad too conventional. With the film, though, I’d argue that Shelton demonstrates there are a lot of ways to push buttons, to challenge expectations. Sometimes it can even be done with warmth and great sympathy for the characters, a desire to understand how emotional wounds are dealt and then healed.