Emma Thost-Hedge was convicted and sentenced in January for charges of affray and property damage, which stemmed from an episode on a Campbell driveway in May 2013.

A man was sitting in his car, preparing to leave the home, when he saw Thost-Hedge, then 21, standing in front of him.

She hit his car and, fearing for his safety, he reversed backward towards the street. He knocked over a friend who was with Thost-Hedge.

That person was badly injured and later died.

The car reversed into a neighbour's hedge, and Thost-Hedge ran towards it, hitting the windscreen with a baseball bat and screaming at the driver.

The man locked the car and called triple zero, before his mother came outside and he went inside with her.

Thost-Hedge pleaded guilty to two charges arising from that incident, and another relating to a property damage some months later, in the ACT Magistrates Court.

The crimes put her in breach of two existing good behaviour orders.

During sentencing, it emerged that Thost-Hedge had experienced a troubled childhood, and had struggled with mental health issues and drug and alcohol abuse from a young age.

A borderline personality disorder was said to have impaired her judgment at the time of the offences.

She was also reported to have improved dramatically since receiving treatment, and the court was warned that incarceration would have a negative impact.

Thost-Hedge was sentenced in the ACT Magistrates Court to six months imprisonment, to serve three months full-time. The rest of the sentence was to be suspended and Thost-Hedge put on an 18-month good behaviour order.

She appealed that sentence to the ACT Supreme Court, saying it was manifestly excessive and deprived her of ongoing counselling and other suitable programs helpful to her rehabilitation.

Thost-Hedge argued the magistrate did not properly consider other sentencing options, such as weekend detention.

Her appeal was successful, and Acting Justice Stephen Walmsley reduced the sentence to three months of weekend detention, followed by a 15-month good behaviour order.

Justice Walmsley found the court had erred by not stating why it had acted contrary to recommendation of a pre-sentence report that deemed Thost-Hedge suitable for weekend detention.

"I have taken into account the history of mental issues involving the offender," he wrote in a judgment published on Wednesday, but delivered in July.

"The affray is a very significant offence, and I consider that the appropriate penalty for that offence, taking into account her subjective circumstances, is to impose a sentence of three months imprisonment to be served by way of periodic detention."

The ACT Supreme Court was also told she had suffered extensively since the offences, particularly due to the death of her friend.

"ACT Health has expressed the view that she suffers every day from the losses in her life, and in particular from the loss of her friend who was killed at the time of the affray," Justice Walmsley wrote.