Katherine Abdallah was found guilty in December at her retrial of the manslaughter of 21-year-old Suzie Sarkis in 2013.

The 36-year-old did not react as she was sentenced in the NSW Supreme Court on Tuesday to a maximum nine years behind bars with a non-parole period of six years and nine months.

Justice Julia Lonergan said Abdallah betrayed the loved ones of Ms Sarkis, whom she had once called her "baby sister".

"This terrible crime has torn the family apart," she said.

The pair had been fighting over Abdallah's new $184,000 Mercedes before she armed herself with knives and killed her relative at her Brighton-Le-Sands townhouse on February 9, 2013.

The night before the death Abdallah told police "she's going to be in serious trouble when I get her" for driving the car without permission and damaging the front wheel.

"You guys will probably be called back," she added in what proved to be an eerily accurate prediction.

Abdallah initially told officers the culprit was a fat, tall Lebanese woman with a tattoo on her hand before claiming self-defence once CCTV footage was found.

She also lied to a triple-zero operator saying she was applying pressure to the wound when she was in fact carefully cleaning the two knives.

The court had previously heard the grieving brother of Ms Sarkis had to visit her grave on his wedding day last year so she could be part of the celebration.

"I don't understand how a person could do this to her family," the victim's sister Christine Sarkis told a March sentence hearing.

"Is that person full of jealousy, is that person full of hatred or are you simply evil?"

Abdallah originally faced a murder trial but was found guilty of the less serious charge of manslaughter and jailed in May 2015 for at least eight years and three months.

Later that year she successfully challenged her conviction and was ordered to face a second trial. She was released on bail in February 2016.

Australian Associated Press