Shakilus Townsend was ambushed by the six-strong gang
A girl must serve at least 10 years in prison for the murder of a 16-year-old boy who was lured to his death in south London in a "honey trap plot".
Samantha Joseph, 17, lured Shakilus Townsend to a waiting gang, which included her ex-boyfriend Danny McLean.
Shakilus, from Deptford, south-east London, was stabbed in Thornton Heath in July 2008, the Old Bailey heard.
Six other teenagers, including McLean, were found guilty of the murder and jailed for life on Friday.
They were ordered to serve a minimum of between 12 and 15 years. Joseph was given a minimum tariff of 10 years.
Brothers Tyrell Ellis, 19, and Don-Carlos Ellis, 18, from Thornton Heath, were convicted of murder, together with Andrew Johnson-Haynes, 18, from Croydon, south London, Andre Thompson, 17, from Norwood, south east London, and Michael Akinfenwa, 18, from Norwood.
McLean, 18, from Thornton Heath, was ordered to serve a minimum 15 years' detention while Thompson was given a minimum term of 14 years.
Meanwhile the Ellis brothers and Akinfenwa were given minimum 12-year sentences.
Johnson-Haynes, a former public schoolboy and London Irish rugby player, was also ordered to serve a minimum 12-year term.
Shakilus, who was "smitten" by Joseph and saw her as his "future wife", was taken to the cul-de-sac where he was attacked with a baseball bat and stabbed several times, including in the chest and liver.
Brian Altman QC, prosecuting, said Joseph, then aged 16, "set up the hapless Shakilus Townsend in a honey trap with a lethal and tragic twist".
Samantha Joseph led Shakilus to the gang, who were masked and hooded
Judge Richard Hawkins told the gang: "You left him to die a lonely death, crying for his mother."
In a victim impact statement, Shakilus's mother Nicola Dyer, 34, said: "My feelings about Shaki's death are a mixture of ever-changing emotions that neither words nor tears can explain.
"I have been robbed of a very rare and precious gem. He was loved, cherished and needed."
She added: "I am unable to understand why these youngsters felt that they needed to use the brutality they did, which, in turn, resulted in my son's life coming to a tragic and abrupt end."
Ms Dyer said she was "consumed in anger" by seeing the defendants "laughing among themselves".
She added: "The reality that these young people with no souls had such a disregard for life that they deliberately conspired to use manipulation to cause nothing short of destruction is absolutely soul-destroying for me.
"I may forgive them one day, but not today."