The teenage girl, who was aged 12 at the time of the assault, Paul Anderson, 37, and 38-year-old Joanna Farrer were each found guilty of two counts of religiously aggravated actual bodily harm following a two-week trial at Woolwich Crown Court.
The victims, a 42-year-old woman and her daughter, 23, were left fearing for their lives after they were attacked by the defendants in Eltham one evening in May last year, the court heard.
A jury was told how the younger victim, who wore traditional Muslim dress include a pink hijab and a long black Abaya, was thrown to the ground by Anderson as one of the other attackers tried to rip off her headscarf.
Her mother was kicked in the stomach and punched in the face by the girl, who cannot be named for legal reasons, the court heard.
On the evening of the attack, the younger victim had been driving along Middle Park Avenue on her way to visit a family member when the girl and a boy who was with her began to cross the road.
Despite there being no zebra or pelican crossing, she stopped the car to allow them to pass and the girl gesticulated towards her.
The victim continued on her way to meet her mother in Eltham Hill and when she stopped the car there, the girl and boy walked past again and the girl began to shout racist abuse.
Her mother told the youths that they had crossed the road in a dangerous spot and an argument began.
The girl attacked the older victim, before walking away and returning with Anderson and Farrer and launching a further assault.
A fourth woman, who has not yet been identified, also joined in the attack, which took place at about 8pm on May 5.
It only ended when the younger victim flagged down a passing ambulance causing the suspects to flee. The victims were left with cuts and bruises.
The suspects were caught by police with the assistance of a taxi driver who witnessed the assault.
Anderson, of Sevenoaks Road, Brockley, was jailed for three years and four months and ordered to pay £2,000 compensation to the victims after all three defendants were found guilty on Tuesday. Farrer, of William Barefoot Drive, Eltham will be sentenced on Friday, April 21, while the girl will be sentenced at Bromley Youth Court on a date to be set.
Detective Inspector Melanie Pressley, of Greenwich Community Safety Unit, said: "This was a brutal and completely unnecessary attack on two Muslim women who were racially abused and then assaulted.
"I have no doubt the attack would have continued had it not been for the passing ambulance one of the victims was able to flag down.
"The victims were left terrified by what happened and lived in fear they would be targeted again. The older victim was too afraid to leave her house for some time.”
He added: “It is shocking that the instigator of this attack was just 12 years old [at the time] and I hope having a conviction to her name at such a young age will be a wake-up call and encourage her to change her ways."