When she followed him down the street to make sure he was leaving, he shoved her against a truck, spat at her again and threatened to trash her on Facebook.
However, defence lawyer George Linder said it was the women who were attacking Fairbrother as he tried to leave the house, and he did not throw a rock at the window.
Sergeant Wayne Corbett said Fairbrother told him the women were making things up, so he posted his version of events to Facebook and 65 people agreed with him.
In court, Fairbrother admitted to the assault and wilful damage after two other witnesses remembered him throwing the rock through the window.
Judge Alistair Garland said he "had the displeasure of listening to what goes on in the social scene of young people in Greymouth" and told Fairbrother to stop turning up to parties uninvited.
Fairbrother was convicted, ordered to pay $40 reparation and sentenced to nine months' supervision, with conditions that he undergo counselling and restrict his use of social media websites.
- The Greymouth Star