Sienna Miller, an actor with more talent than she’s often given credit for, is frequently lumbered with waity-wife supporting parts. But now she finally finds a starring role worthy of her in American Woman, a serious, emotional drama by Jake Scott (son of Ridley).

Miller is utterly believable as a woman in working-class Pennsylvania whose teenage daughter disappears. The grief-stricken mom is familiar from dozens of dramas, but working with a sensitive script by Brad Ingelsby, Scott has a made a film about living in limbo with uncertainty over years – though the increasing focus on his character’s romantic relationships gets a bit soapy.

Miller is Debra, a supermarket checkout worker who got pregnant at 16, to the shame of her Irish Catholic family. Her daughter, Bridget (Sky Ferreira), is now 17 with a baby of her own. Debra has a reputation in town as being a bit trashy, but like Erin Brockovich she’s got a brassy resilient streak. When Bridget vanishes after a night out we get some pretty bog-standard missing-kid drama.

The action then skips ahead five or so years. Bridget is still missing and Debra is raising her grandson. She’s finally growing up, back at college, where she is learning accountancy.

The film spends a lot of time on Debra’s love life – first with a controlling boyfriend, then, a few years later, marrying a younger guy (Breaking Bad’s Aaron Paul) – before finally getting round to resolving the mystery of who took Bridget.

Its grace is how attuned it is to ordinary lives. Despite featuring big-name actors – Miller, Paul and Mad Men’s Christina Hendricks as Debra’s sister – American Woman is a film with a lived-in authentic feel. And Miller plays it beautifully with psychological depth and not a jot of actorly condescension.

This has got to be her platform for landing better roles.