Bird (Sherman Cymru, Cardiff)

One month shy of her 16th birthday, Ava is about to fly the nest. Having grown up in a care home, she'll no longer be a fledgling, but it's equally clear that she's not yet a bird – a term that, applied to women, suggests a brassy confidence, even as it demeans and objectifies.

Katherine Chandler's play, one of the Bruntwood Prize winners in 2013, examines her vulnerability, how exposed Ava is to the elements. After three years without contact, her mother rejects her, refusing to accommodate her daughter into her new family and, with nowhere to go, Ava seeks someone to cling to. It's a dangerous situation; one that means needing to please. "Tell me what you want and I'll do it," she says to a boy, Dan, she meets kicking about in the park. He does. So she does.

It's that cabbie Lee (Guy Rhys) latches onto, buying her booze, food and flashy phones, half-listening when no-one else will. He offers her a room and, on her 16th birthday, gets dressed up to the nines: his best cowboy shirt and boots – a particular posture of masculinity. That threshold of legality – yesterday, a child; today, an adult, capable of consent – seems so arbitrary and indistinct.

Chandler portrays the grooming process carefully. Lee's a creep, but his intentions aren't exactly clear-cut. It often looks like Ava's coming onto him, naively offering what she assumes he wants, almost out of politeness. When she places a hand on his crotch, he scolds her: "It's cheap." The combination of gift-giving and guilt is toxic, but potent.

Bird skitters about as much as its protagonist and, though it signals its plotting, its purposes aren't entirely straightforward – complex, but cluttered as well. Ava's haunted by her best friend and roommate, Tash (Rosie Sheehy), who recently committed suicide and talks of stars and escape, and her exchanges with Connor Allen's mournful Dan and her mother (Siwan Morris) don't entirely fit together.

Partly, it's obscured by over-extended bird metaphors. A whole flock of them flutter through the script and, though often poetic, they have the effect of 'artsifying' Ava's experiences. Rather than a truthful testimony to the sort of life that often gets overlooked, you become acutely aware of watching an artist's impression of it – a writer wringing beauty out of something grim.

However, Chandler's tenderness, her affection for Ava, just about keeps exploitation at bay, and Rachel O'Riordan's production extends that care. She's a beautifully drawn character, Ava; a knot of contradictions. Knowledgeable in some respects, ignorant in others; wide-eyed with wonder but guarded too. She flits from overt sexuality to gawkiness, and Georgia Henshaw, always twitching and rearranging herself, catches both her vigour and her vulnerability.

Bird runs at the Sherman Cymru, Cardiff until 28 May.