An out-of-control Cromwell teenager who threw a meat cleaver at another person has been convicted of assault.

Hannah Birch, 17, threw the cleaver after an argument, missing her victim by a metre with the chopping implement becoming embedded in a wall.

She was yesterday convicted of assault with a weapon in Alexandra District Court and ordered to come up for sentence if called upon within 12 months, the Southland Times reported.

Lawyer Tim Cadogan said Birch had been doing her best to become a better person, and requested a discharge without conviction.

But Judge Stephen O'Driscoll denied the request, saying he hoped the sentence would encourage her to stay out of trouble.

He said Birch had been out of control and made a one-off mistake.