Natalie Edwards was spotted repeatedly beating the man in the parked Ford C-MAX, in Harworth, at 10.50pm, on September 30.
A witness described the man being struck at least ten times “as hard as she could make them,” said prosecutor Donna Fawcett.
Police were later called to an address on Devonshire Drive, where Edwards was arrested after the man was seen with various injuries.
“She had a lot to drink and doesn’t remember assaulting him. She couldn’t explain an injury to her right hand,” Mrs Fawcett added.
Fiona Davidson, mitigating, said Edwards was a vulnerable young woman who had been in the relationship for a number of years, but only began to drink in the last two years.
“She has been the victim of domestic violence in the past, but had made no complaints to police,” she said.
She said Edwards had since referred herself for anger management and alcohol treatment, and her partner, who did not make a full statement, wants her to return.
Edwards, 24, of Lowtown Close, admitted assault by beating, when she appeared at Mansfield Magistrates Court, on Wednesday.
District judge Jonathan Taaffe said: “It strikes me that drink is the issue here for both parties.
“It’s clear to me that when you drink problems arise.”
He handed her a two-year conditional discharge and ordered her to pay £85 costs and a £20 government surcharge.