The summary of facts, which were not read out in court, said the act happened about 7.49pm on October 27.
After they had ordered food, Ainge, who was a passenger in the car, performed the sexual act.
''The act was performed in clear view of the victim who served the food,'' the summary said.
After the judge said how the act must have impacted on the worker, he said he did not need to say much more.
"I think you know from your reactions in court today, there are no explanations for this other than you were grossly intoxicated."
She was sentenced to 12 months' supervision and ordered to pay $250 in emotional harm to the victim.