A jury in Versailles yesterday set a sentence exceeding the 12 years demanded earlier by the prosecution for Jessica Davies.
The court had heard how Davies, 30, met the 24-year-old man in a bar in November 2007 and then went with him to her flat.
Later that night she called police, who found the student bleeding from knife wounds to the throat – the same knife which Davies had used months earlier in a suicide attempt.
Davies admitted stabbing him, but insisted her memory of events had gone into "a black hole".
She faced a maximum sentence of 30 years in prison, if convicted of "unpremeditated voluntary homicide".
The court heard that she met student Olivier Mugnier by chance in a bar after a day drinking in Paris. They both went back to her flat, where she called police after stabbing Mr Mugnier in the throat.
She told the first officer on the scene: "It's me who did that, I'm a monster."
Yesterday, before sentencing, UK-born Davies, whose businessman father is Quentin Davies' brother, expressed her remorse and said she took responsibility for what happened, even though she could not remember the details.
Prosecutor Myriam Quemener criticised Davies' "selective memory" but said the defendant's personality problems had to be kept in mind.
Davies has admitted that she has experienced long-term problems with drink and drugs – the result, she claimed, of emotional problems triggered by the separation of her French mother and her father.
The court heard that the knife used in the attack on Mr Mugnier was the same one used by Davies in a suicide bid three months earlier.
A police report read out in court said she told officers who arrived in response to her emergency call on the night of the stabbing: "It's me who did that, I'm a monster.
"I wanted to cut him a bit and it went right in."
Mr Mugnier was discovered naked and bleeding from throat wounds – with Davies trying to stem the flow. He died soon after medical help arrived.
Davies, who allegedly fetched the knife after the couple, both drunk, had abandoned efforts to have sex, had mixed alcohol with prescription drugs – a combination which could have triggered aggression, the jury was told.
Her mother Monique Henry told the court her daughter had been upset by family problems and had turned to drink in her teens.
Davies has vowed never to drink again.