The girls, then aged 17 and 13, bullied and beat up Rosimeiri Boxall, 19, just before she died in May last year.
The prosecution at London’s Old Bailey said she plunged from the third-floor window to escape their abuse.
Kemi Ajose, now 19, and Hatice Can, now 15, were found guilty of manslaughter, the Press Association reported.
After the verdict, Boxall’s family said they forgave the pair responsible for their daughter’s death.
“Forgiveness means that we refuse to be shackled by bitterness and our prayer is that forgiveness will allow the girls to be released from the burden of what they have done, so that they can even now grow into the sort of people that God intended them to be,” the statement said.
During their trial, the girls had blamed each other for telling Boxall to jump when she climbed up to the window after she was attacked.
Witnesses said Can had shouted insults at her as she lay dying. Part of the attack on Boxall by Ajose was filmed on a mobile phone by a neighbour and played to the jury.
The court heard the sound of her being slapped and punched while her hair was pulled and hairspray was aimed at her face. The two girls had been best friends but fell out as an argument between the younger girl and Boxall about a boy escalated to comments about family backgrounds.
Boxall had gone to stay at Ajose’s new flat in Blackheath, southeast London, which had been given to her under a social services scheme and was later joined by Can, who had run away from home. Can took against Boxall when she hit it off with a boy who came to the flat. Fuelled by vodka, the argument turned violent.
Can admitted assaulting Boxall but both girls said they were not there when she fell.
After her arrest, Ajose said Boxall asked “Do you want me to jump?” and the 13-year-old answered: “Yes”.
“Rosie leapt to her death from the kitchen window of Kemi’s flat to escape from a prolonged period of physical and verbal abuse,” said prosecutor Roger Smart. “Immediately before Rosie fell, she was clearly in fear of being hurt physically.”
As she lay dying of multiple injuries, Can said: “Serves you right, bitch”.
Boxall, whose adopted father ran a community church in Thamesmead, southeast London, had left home the previous year. She was adopted at the age of three by her missionary parents after being abandoned in an orphanage in Brazil by her alcoholic mother.
Both girls, who had no convictions but had been cautioned by police, were remanded until December 15.
