Knox councillor Joe Cossari told SBS the attack was reported to the Knox Multicultural Advisory Committee by a teenage member of the committee who attends high school with the victim.
He said the victim had been wearing a hijab when she was "punched to the ground on her way home from the Westfield shopping centre."
After hearing of the attack, which he "assumed" was racially motivated, Councillor Cossari reported it to the council.
He refused to name either women, or the high school they attended, but said he had raised the attack publicly to prevent similar incidents taking place.
"We cannot tolerate this kind of behaviour in our society," he said.
Councillor Cossari said it was the first time in almost five years with the City of Knox that he had heard of such an attack.
But Islamic Council of Victoria spokesman Mohamad Tabbaa told SBS that attacks against Muslim women were not uncommon.
He said the council heard numerous complaints of verbal abuse and harassment, as well as physical assaults.
"Sometimes it's only one [attacker], or sometimes it's a small group," he said.
Councillor Cossari said the girl has not reported the attack to police "because of fear of ramifications," but Mr Tabbaa said the council was working to find the girl and had offered to report the incident on her behalf.
Victoria Police confirmed they had not been notified of the incident.