Gemma O’Doherty has been convicted of threatening and abusive behaviour, as well as refusing to give her name and address to a garda.
She was also found guilty of resisting arrest.
Ms O’Doherty appeared in court in Bray on Wednesday in connection with an incident on the footbridge on the N11 at Kilmacanogue in Co Wicklow last August.
More than 30 supporters of the 53-year-old, including John Waters, gathered outside Bray Courthouse to support Ms O’Doherty.
Judge David Kennedy handed down a two-month suspended sentence and a fine of 750 euro for the public order offences, which occurred in August last year.
Ms O’Doherty has already lodged an appeal against the conviction.
The crowd, which gathered at around 10am on Wednesday and remained until nearly 6.30pm, carried anti-vaccination placards and shouted support for Ms O’Doherty throughout the day.
Ms O’Doherty was applauded and cheered by her supporters as she left the court on Wednesday evening.
Solicitor Brendan Maloney told the court that the incident occurred against the backdrop of a campaign in which his client is deeply invested.
“We were told we were traitors to the Irish public and that we were complicit with cover-up of paedophilia, and complicit in the cover-up of murder,” Garda Andrew Sullivan told the court.
“She said we would get the sack and she said our pensions would be gone.”
He said that the defendant refused to give her name and address.
“He moved to arrest her and she tried to walk off the bridge.”
Signs on the bridge at the centre of the incident read “masks spread virus” and “no forced vaccines”.
“We remained calm throughout,” Garda Sullivan said. “They had a right to protest – that wasn’t disputed. I expressed concern for the motorists below.”
Garda Joseph Waldron gave evidence regarding arresting Ms O’Doherty after attempting to take her name and address.
Judge David Kennedy said that the words she used towards gardai were “atrocious, and they were said deliberately”.
“She called them gangsters, thugs, said that they covered up paedophilia, they were traitors, and covered up murder.”
The judge said it was a clear and intentional breach of the peace.