.
Arsema Dawit, 15, was knifed more than 50 times by Thomas Nugusse in central London in June 2008, less than two months after she told police he had attacked her.
An inquest into her death has heard that she and her family reported the beating in April that year, but feared at the time that nothing would be done.
The inquest heard Arsema, her mother Tsehynesh Medhane and cousin Melyon Isak went to London's Kennington police station in April 2008 after Nugusse slapped her in a McDonald's.
But Miss Isak told the inquest that, after speaking to station receptionist Gillian Johnson, she felt the police were not taking the threat Nugusse posed seriously.
She said: 'I remember giving her all the proof that we had and her asking for more proof. I did not think that anything would be done.'
She told the inquest: 'When I said that she [Arsema] had been assaulted she [Ms Johnson] kind of laughed and said in a joking kind of way "why did you let him do that to you?" with a smile on her face.'
The hearing was told that, even while the family were at the police station, Nugusse texted Miss Isak with the warning 'stay out of it don't get involved'.
Mrs Medhane asked the police 'to arrest this person and [make] my daughter safe', jurors heard.
Police at the block of flats in Waterloo, central London where the 15-year-old's body was found stabbed in 2008
Ms Johnson told the inquest today that, despite Arsema's age, the incident was not recorded as child abuse or domestic violence and was instead investigated as an assault.
She said: 'A domestic is when two people are in a relationship and there's an assault within the relationship. It goes to a different unit that deals with domestic violence.
'A domestic is anybody who is over 17 in a relationship... She was too young so it wouldn't be domestic violence.'
Arsema's body was found by neighbours in a lift in the flats in a tower block in Waterloo on June 2 2008. A knife was also found in the lift.
After his arrest, killer Nugusse, then aged 21, was found hanging in his cell on 24 June, but prison staff managed to revive him.
Nugusse, formerly of Ilford, Essex, was left severely brain damaged and now needs 24-hour care.
He was too unwell to be tried but was found to have committed the act by a jury five years ago and detained indefinitely under the Mental Health Act.
The inquest, which was called after Arsema's family went to the Independent Police Complaints Commission, continues.
