A mother who confessed to drowning her three children by deliberately driving her car into a Melbourne lake has had her jail sentence slashed by more than eight years.

Akon Guode, a Sudanese refugee, was jailed in 2017 for a total 26 years and six months, with a non-parole period of 20 years, after pleading guilty to the infanticide of her one-year-old son, Bol, and the murders of her four-year-old twins, Hanger and Madit, in April 2015.

She also plead guilty to the attempted murder of her six-year-old daughter, Alual, who was pulled from the wreckage and survived the crash into the Wyndham Vale lake in April 2015.

Akon Guode, 38, was last year sentenced in the Victorian Supreme Court to at least 20 years jail after pleading guilty.

The Court of Appeal today reduced her sentence to 18 years, with a non-parole period of 14 years, because of her "disturbed state of mind" when she committed the crime.

Guode arrived in Australia as a Sudanese refugee after being repeatedly raped and witnessing the execution of her soldier husband.

While handing down his sentence in May last year , Justice Lasry said Guode did what she did out of "extreme desperation."

"Your life was in turmoil," he said.

Guode plead guilty to the infanticide of her one-year-old son, Bol, and the murders of her four-year-old twins, Hanger and Madit.

"In my opinion you were shocked by what you did... but there was nothing involuntary about your actions."

Justice Lasry said Guode's life in Sudan before moving to Australia caused her to suffer post-traumatic stress disorder.

"You watched your husband be shot to death before being repeatedly raped until you were unconscious," he said.

"In some respect, this sentence is inadequate but at the same time excessive for what you have been through".

"This was a horrendous crime on innocent children."

The 4WD being removed from Lake Gladman in Melbourne. (Nine)

Akon Guode at the funeral service for her three children before being charged with their murder. (NIne)

"It was a total betrayal of trust".

Guode faces possible deportation at the end of her prison sentence.

After Guode drove into the lake, she tried to blame her lover's wife, who she said used a witch-doctor to place her under a "dizzy spell".

The community rallied around the then 35-year-old, held vigils for the slain children, and raised money to cover funeral costs.

Four months later, Guode was charged with three counts of murder, and one of attempted murder.

She was remanded in custody, and in December 2015 she cried and begged a magistrate to let her go home but bail was refused.

The community rallied around the then 35-year-old, held vigils for the slain children, and raised money to cover funeral costs. (Nine)

CCTV footage was played in court that showed her car driving past the lake not long before she drove into it.

The security cameras captured the vehicle driving past the lake at least five times before it quickly turned, mounted the kerb and drove into the water.

Dozens of witnesses gave evidence against Guode, including a collision investigator who said the car was deliberately driven into the water.