Lisa Borch, then 15, and her boyfriend Bakhtiar Mohammed Abdulla, 29, stabbed her mother Tina Römer Holtegaard at least 20 times in their home in Kvissel, northern Denmark, in October 2014.

Before the brutal murder of her mother, Borch had spent hours on YouTube watching footage of the savage decapitations of David Haines and Alan Henning.

The 16-year-old will serve nine years in prison - the longest sentence handed to a teenager in modern times in Denmark - after a High Court upheld a September ruling.

Borch had appealed her initial sentence, telling the Western High Court that the plan to kill her mother was all Adbulla's idea,

She told the court she had only confessed to the crime because she was scared of her boyfriend, who at 29 is nearly twice her age, The Local.dk reports.

Her stepfather Jens Holtegaard told Danish media that although Borch was obsessed with ISIS, she could 'just as easily been attracted to the biker gang environment or some other extreme'. 

During the initial trial in September, the court heard how Borch became obsessed with the terrorists’ activities after falling in love with her boyfriend.

Following the brutal murder, in which both Borch and Abdulla participated, the teenager called police claiming: 'I heard my mother scream and I looked out the window and saw a white man running away. Please come here, there is blood everywhere.'

On arrival police found Mrs. Holtegaard, whose husband was away on a short business trip at the time of her murder, covered in her own blood in bed.

Despite making the frantic phone call, the victim's daughter was discovered sitting on a chair in the living room playing with her iPhone and watching videos on YouTube. When police asked where her mother was, Borch refused to leave her computer and simply pointed upstairs.

A later police examination of the computer showed that she had watched endless repeats of the beheadings of the two Britons, both of whom had been in Syria.

'She watched them the whole evening long,' said prosecutors at her trial. When police first arrived at the house she didn't leave the computer and merely pointed upstairs to indicate where her mother lay dead. It was this apparent disinterest which made her prime suspect in a matter of minutes.

The court heard that Borch's twin sister had recently moved out of the family home because she couldn't stand the constant arguing that went on between her mother and sister.

Prosecutors said it was this 'endless rowing which cost the mother her life.'

The court was told that Borch had teamed up with Abdulla after being dumped by her first lover. The two planned to flee together to Syria and fight for the ISIS terrorists.

Borch claimed at the trial that they were 'just good friends' but authorities believe they were lovers.

The rows with her mother intensified as she pressured her daughter to break off her relationship with him and 'live the life of a normal teenager.'

Prosecutor Karina Skou told the court that the pair made a diabolical pact to kill her mother saying: 'This murder was cold blooded, ice cold and committed in a bestial manner.'

Borch even showed her twin sister the knife she planned to use to kill their mother, but the comment was incorrectly written off a macabre joke.

He claimed to have only arrived to 'help Lisa' after the teenager had already killed her mother. But Borch said Abdulla had actually been the knifeman.

The muddled version of events meant the court heard several stories about what actually happened.

Although Abdulla was no longer at the property when police arrived, investigators found his fingerprints in the victim's bedroom.

Although it couldn't be established who'd actually delivered the blows that killed Mrs. Holtegaard, both of the accused were found guilty of murder.

Borch was sentenced to nine years in prison, the first of which will be spent in a youth offender’s institute.

Abdulla received 13 years and will be expelled from Denmark when his sentence is up.

Both were ordered to pay around £40,000 in compensation to Mrs. Holtergaard's husband - Borch's stepfather - as well as her twin sister and a younger brother.

Borch's twin was in court to see her sister sentenced but did not look at her during the trial, DailyMail reported.

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