A Danish girl who stabbed her mother to death after becoming obsessed with ISIS beheading videos has been sentenced to nine years in jail.

Lisa Borch was 15 when she committed the sickening crime along with her 29-year-old Iraqi boyfriend Bakhtiar Mohammed Abdulla in October last year, The Daily Mirror reports.

The court heard that the teen had been watching the gruesome videos just 15 minutes before stabbing her mother Tina Römer Holtegaard at least 20 times at the home they shared in Kviseel, in rural Denmark.

Borch then called police yelling that she heard her mother's screams and seen a white man running away from the home.

When police arrived at the home they found Ms Holtegaard covered in blood and a short time later discovered Borch in another room calmly playing with her phone.

When police examined her computer they learnt that she had been watching the beheading videos.

Prosecutor Karen Skou said "This murder was cold blooded, ice cold and committed in a bestial manner."

The court heard that Borch fell in love with radical Muslim Abdulla after meeting him at a refugee centre near her home.

The pair allegedly discussed fleeing to Syria to join ISIS after killing Ms Holtegaard.

Borch blamed Abdulla in court but he argued that he only arrived at the home after the fatal stabbing to "help Lisa".

When police arrived at the home Abdulla was not there but his fingerprints were found in the mother's bedroom.

Police were unable to determine who delivered the fatal blows and both were convicted of murder.

Borch was sentenced to nine years in jail. She will spend the first year in a young offenders institution.