Juna Suleiman’s documentary about Hiam, her octogenarian grandmother who lives in Nazareth, is no journey through a picture-perfect family album. Hiam is not the cake-baking kind of grandmother. In fact, she is grumpy, foul-mouthed and very politically incorrect. It could have been quite annoying to spend more than an hour with someone so disagreeable, and yet Suleiman’s love for her grandmother’s quirks shines through, making this familial snapshot an interesting watch.

First off, Hiam is not the sister of that Mussolini. For reasons untold, her parents named one of her brothers after Il Duce. Another child, named Hitler, died in infancy. Still, the film does not dwell much on Hiam’s younger days, and instead focuses on her day-to-day activities, which include berating her ever-changing cleaners, venting bitterness about the news, and lamenting her son’s rare visits. Mostly shot inside Hiam’s apartment, the film acquires an undeniable sense of claustrophobia, which renders her bitterness understandable rather than unforgiving. Instead of turning a senior citizen into a one-dimensional cliche, the decision to capture both Hiam’s humour and her unpleasant side gives us the fullness of her personality. Hiam may look harmless, but you would think twice before crossing her.

And what humour! It is not so much her jokes but the matter-of-fact way Hiam describes daily events that makes her a hilarious person to watch. At one point, she admires a cereal brand because it gives her regular bowel movements. While Hiam’s rambunctious character may get a bit much at times, this compact documentary acutely zooms in on the loneliness of old age and the fierce resentment it can cause. Underlying Hiam’s cutting remarks is perhaps a desire to connect and to be listened to.

• Mussolini’s Sister is available on 24 September on True Story.