The court also heard Williams was working at a care facility, which would be forced to let the teenager go if she had a black mark on her record.
Counsel John Farrow said his client used the money from the job to pay for her university psychology studies.
If she lost employment, her intellectual pursuits would be jeopardised, Judge Kevin Phillips said.
While Williams was a "sought after" model in Dunedin and Queenstown, the judge said travel for potential international assignments would also be hampered by a conviction for violence.
On August 27, 2016, the defendant arrived at a party to find her then boyfriend extremely drunk, arguing with another man.
That man, and others at the party, were people Williams had clashed with when she was bullied at high school.
Judge Phillips said the defendant pushed the victim and he pushed her back.
He then called her a "slut".
Others in the victim's group told Williams no-one liked her.
She reacted by striking the man in the back of the head with a wine bottle. A woman sustained a gash to her hand in the melee.
The judge said it was clear there was a protracted background to the incident.
Williams had health problems when she was younger and moved schools, where she was targeted by bullies.
"This is not one night's angst," he said.
Both victims had suffered as a result of the incident, the court heard.
The man had endured stress and anxiety for more than a year, while his female counterpart had to pay for medical treatment to her wound and had missed out on study time.
Judge Phillips assessed the gravity of Williams' offending as "moderate" but he said it was outweighed by the likely consequences she would suffer with a conviction to her name.
She was a teenager, had significant prospects and an unblemished record, the judge noted.
He granted her a discharge without conviction on condition she could prove she had initiated psychological counselling.
Williams was also ordered to pay each victim $750.
