For many years, Australian pop star Sia has hidden behind a fringe that covers her eyes. Using actors instead of starring in her own music videos, she has preferred not to centre herself. Yet her directorial debut appears to draw from her own experiences with addiction; its protagonist Zu (a near-bald Kate Hudson) is a recovering alcoholic. This is confusing, given that the film’s title refers to her non-speaking, neurodivergent younger sister Music (Maddie Ziegler), whose main purpose is to absolve Zu from her troubled past.

Ziegler, who appeared on the reality TV show Dance Moms, and features in some of Sia’s best-known videos (including Chandelier and Elastic Heart), is not herself on the autistic spectrum. It’s a problem, especially given the cartoonishness of her portrayal, which sees her gurning, grimacing and mumbling through her scenes. Music uses an augmentative and alternative communication device to translate rudimentary expressions such as “I am happy” and “I am sad”. Her interior world is just as simplistic, conveyed via goofy musical interludes rendered in childlike primary colours and abstract shapes. The lyrics, jaunty platitudes about Music’s “magic mind” and failing body, are offensive too. These self-consciously upbeat moments clash horribly with the wider redemption narrative.

• Available on multiple VOD platforms from 15 February