Irene Elizabeth Fairbrace (43) appeared in the Magistrate’s Court last week.
CCTV footage captured the incident, at 20:50 on 17 March, in which she struck the staff member in The Caesarea pub in Cattle Street.
The barman was left with minor bruising but no serious injuries.
Fairbrace admitted the assault and told the Magistrate’s Court: “I do regret what I did. I’m not normally like that.
“It was a moment of madness.”
She added that she was usually a moderate drinker, but said: “I had had a bad day and I was drinking vodka. I am not normally that intoxicated.”
The Magistrate, Bridget Shaw, said Fairbrace’s early guilty plea and the fact that she was at low risk of reoffending allowed the court to impose a community sentence of 50 hours. She was also given a ban from the Caesarea for three months.