A Manitoba provincial court judge is being urged to impose a seven year adult sentence for the teen who led the fatal attack against Serena McKay, a 19-year-old high school student beaten and left to die by her peers.

Crown attorney Jennifer Comack told court on Monday that sentencing the girl as a youth, which carries a maximum sentence of three years, would be too lenient.

"When you watch those videos, you will not see an adolescent," Comack told the judge. "You will see a woman, full of rage, beating on a helpless victim."

McKay's body was found on Manitoba's Sagkeeng First Nation on April 23, 2017. A pathologist said she likely died from hypothermia, unable to seek protection from the cold because of her injuries and the amount of alcohol in her system. Two teenage girls, who were 16 and 17, were arrested.

The older teen was sentenced earlier this month to just over three years in jail. The younger girl, who has since turned 17, pleaded guilty to manslaughter in January and was in court Monday for a sentencing hearing.

Teen photographed covered in blood and smiling, court heard

The Crown played two videos of the attack on McKay in court that show her being repeatedly punched and stomped on by her peers. The younger teen can be heard saying, "I don't want to f--king see her alive," said Comack.

Later that evening, court heard the teen appeared in a Snapchat photo, covered in blood and smiling, with the tag line "just chilling."

As the videos played, the girl sobbed in the prisoner's box.

Comack told the court, the day after the attack the teen tried to pretend nothing happened and asked her co-accused to lie for her and say she didn't fight Serena that badly.

"This wasn't a one-punch fight, or even a two-punch fight," the Crown attorney told the court. "She beat Serena's face until it was unrecognizable."

McKay endured 67 injuries

Court heard that McKay had 67 injuries to her body when she died.

The Crown argued the girl's behaviour prior to the attack was indicative of someone who was making adult decisions for herself despite her family's rules and efforts to steer her on a better path.

Court heard the teen was raised by her mother on a First Nation near Calgary and had an "extremely good" childhood. She later moved to Sagkeeng First Nation, where she began experimenting with alcohol and drugs at age 15.

A Manitoba provincial court judge is being urged to impose a seven year adult sentence for the teen who led the fatal attack against Serena McKay, a 19-year-old high school student beaten and left to die by her peers.​ 1:40

Comack said the girl's mother described her a rebellious teenager, who began skipping school and living on her own at age 16. Court also heard she struggled with alcohol and drug abuse.

However, the Crown attorney told court the girl was raised to know right from wrong and had no reported cognitive disabilities.

​"A youth sentence will not be long enough," Comack told the judge, adding a pre-sentence report labelled her as a high risk to re-offend.

26 victim impact statements

In the days following McKay's death, video of the attack was shared widely on social media. Comack said the beating "shocked and disgusted an entire country."

She submitted 26 victim impact statements from family members, friends and even strangers who had watched the video and said they were emotionally impacted by McKay's death.

McKay's mother Delores Daniels told the teen's sentencing hearing that her body and mind cannot rest since losing her only daughter.

"Losing her is always in the back of mind," Delores Daniels told the court. "I dream about her and I wake up crying and sad that she's not here."

Judge Lindy Choy will decide whether to consider the victim impact statements written by strangers before proceeding with the defence's submissions on Tuesday.

The older girl, who has since turned 18 but can't be named because she was underage when the beating occurred, pleaded guilty to second-degree murder in December.

She was sentenced as a youth to just over three years in jail followed by roughly two years of community supervision.