Paula Buchan had grabbed the schoolgirl - whose identity we cannot reveal - after she was involved in a scuffle with her daughter, Courtney.
The menacing mum gripped the child and ordered her daughter to 'punch her puss'.
After admitting the attack outside the Morgan Academy school in Dundee, Buchan was fined £100 by Dundee Sheriff Court last week, but the mother of the beaten girl said that by pleading guilty one week before the trial 'her word was never challenged'.
The devastated mum said she had been left in tears when she saw the video of her 'wee girl' being attacked.
The fight is thought to have kicked off after a week of 'funny' looks and 'cross words' in the school corridors.
The battered girl's mum told the Scottish Sun: "The week before all this happened there had been a funny look and some cross words between them in the corridor. After school that day my daughter was chased down the street by this woman who asked her where she lived, because she was going to come round to our house and beat me up."
She went on to say that when approached, Courtney denied she wanted to fight the other girl, but the girls were 'put in a position where they were to fight' after rumours and gossip continued to circulate.
Buchan, 39, claims she only stepped into the fracas because her own daughter had been bullied, something that the victim's mum denies.
The video shows the girls grappling and pushing each other before exchanging blows. Buchan then appears and grabs the other girl by the throat. She can be heard shouting to her daughter "Come here and punch her puss now" and then "Just f***ing hit her" before her daughter punches the girl.
The fight was finally ended when other pupils pulled Buchan off the youngster.
Buchan's defence lawyer, George Donnelly, said she had complained to the school repeatedly about Courtney being bullied, and that 'emotion' took over when issues were not resolved.
The other girl's mum insists that her daughter is not to blame, saying: "My daughter is not a bully. She is more likely to stand up to bullies and she knows not to hit anybody - although she's not going to stand there and let someone knock seven bells out of her. All she did was stand her ground."
Buchan admitted the assault and breach of the peace last November.
This is just SO shocking. What kind of mum not just allows this to happen, but actively encourages it?