After making music videos for big names like Radiohead, Oasis and Massive Attack and directing two tepid features (PLUNKETT & MACLEANE and WELCOME TO THE RILEYS), director Jake Scott rolls up his sleeves for his new female-led feature AMERICAN WOMAN (co-produced by his dad Ridley Scott).

With its dysfunctional family dynamics and washed-out suburb aesthetics, AMERICAN WOMAN doesn’t re-invent the wheel of contemporary US social realism, but it hits the zeitgeist hunger for no-frills girl power on screen and offers a potent stage for lead Sienna Miller to give the performance of her career.

Miller stars as Debra Callahan, who is already a grandmother at 32. Living with her teenage daughter Bridget (synth pop singer Sky Ferreira) and grandson Jesse somewhere in Pennsylvania, Debra scrapes together the energy that’s left after her supermarket shifts to glam up for dates in a motel with a married guy. When Bridget doesn’t come back home after a night out, Debra goes on a long, teeth-gnashing mission to find out what happened and pulls herself through stages of grief, anger, defiance, despair and, eventually, peace of mind.

Sienna Miller, often folded into neat supporting roles despite her extended filmography, is a real force of nature here: in her hands, Debra’s quick and erratic temper matures into a super-palette of 1001 clean-cut emotions. When using a frying pan filled with scrambled egg to defend herself against an abusive boyfriend, Miller’s performance takes your breath away.

While some one-liners dig deep into the melodrama cliché (“What didn’t I give you?” asks the cheated-on Debra with her cigarette between her fingers), Brad Ingelsby’s script is generally both intimate and engaging, rising to full power when Debra and her older, conscientious sister Katherine (a compelling Christina Hendricks) tease each other with so much prickly love it’s almost combative.

Although the narrative unfolds with comfortable linearity through stages of lost and found love, a new start, death, marriage and extensive nagging and caterwauling, the dramatic curve’s juices tend to dry up temporarily when one event is crammed in after the other. Often, editor Joi McMillon (otherwise celebrated for her work on Academy-Award winner MOONLIGHT) reduces us as an audience to onlookers rather than participants in Debra’s life: as we’re about to dig ourselves into a scene’s emotional grit, we’re already yanked out of it with race horse speed.

Cinematographer John Mathieson (MARY QUEEN OF SCOTS, GLADIATOR) creates the washed-out, grainy colour palette and un-artsy framing that matches the aesthetic of WINTER’S BONE or MANCHESTER BY THE SEA, but this doesn’t quite fit the intimacy of the family’s seething tensions and Debra’s fragility. The film’s soundtrack is equally hit-and-miss: sporadic, unimaginative stock piano chords recall massage CDs instead of something more tailor-made, while a climactic scene in a muddy field towards the end uses slowly swelling drones to more powerful effect.

AMERICAN WOMAN is a flawed and tough watch, but Sienna Miller’s kick-ass performance shines with enough pride and resilience to smooth out the jumpy narrative and technical scratches.