In an early scene, in The Gardener and the Dictator, the 87-year-old Ms. Kaui reveals herself to be a virtuoso of the elder-relative guilt trip. Staring into the camera, she tells her adult granddaughter, Toronto-based filmmaker, Jane Hui Wang, “If you love your grandpa, don’t leave until you bury us.” Ms. Kaui, a comically bossy matriarch whose family affectionately calls her a “dictator,” ruled a one-bedroom concrete-walled apartment in the central Chinese city of Wuhan.