Her boyfriend, who declined to be named, said the attackers were aged 17 and under, and were mainly girls.
The girls punched Medea, knocking her down before they kicked her in the face and body as she lay on the ground, he said.
Another small group of teenage boys held him back from stopping the attack, he said.
"I jumped in but got pulled out. I was pushed and shoved but nobody hit me."
He said the incident may have been recorded on a cellphone that one girl had been holding during the attack.
Medea said she knew two of her attackers but the others were strangers.
Her mother, Belinda Goodwin, said her daughter was unaware of the extent of the injuries until she woke up on Sunday.
She took her to Wairarapa Hospital and a CAT scan showed she had a skull fracture.
Mrs Goodwin said her daughter was the latest victim of teen gangs on Masterton streets after dark at weekends.
She was the second person in her circle of friends to be attacked after a Makoura College schoolboy was beaten and hospitalised two weeks ago.
Police had taken photos of Medea's injuries and interviewed her and her boyfriend.
Mrs Goodwin said she was keen for a family group conference involving the suspected offenders and their families, although her daughter was uncertain whether she would attend.
Masterton police detective constable Maureen O'Leary said she was leading an investigation into the assault but declined to say if charges were pending.
