A film about the leader of The Shakers, an 18th century religious group, uses songs and dancing to portray the fervent spiritual forces at work in the nonconformist Christian movement. We don’t see many film dramas about devoutly religious people—partly, I think, because the main action takes place inside a character, and this is hard to depict on screen. Mona Fastvold faces that challenge head-on in her new film portraying the life of the leading figure in the history of the Shakers: The Testament of Ann Lee. Amanda Seyfried plays the title role of Ann Lee, a young woman in…