Karen Peterson, 29, was charged with assaulting 26-year-old William Eden on April 19, 2019 at Future Fitness in Shawlands, Glasgow.
Mr Eden claimed that he had treated Mr Peterson as if he were treating an injured client.
He said the couple went to the staff room where they were allegedly pushed before falling to the floor.
Mr Eden claimed he spat blood and later received metal plates for a broken jaw.
“The injury is the worst pain of my life,” he said.
Petersen, meanwhile, claimed that Mr Eden had tried to attack him and that no one had escaped.
A jury in Glasgow Sheriff’s Court has ruled that the attack was a serious injury, a permanent defamation and a permanent misdemeanor.
Petersen had earlier filed a special defense lawsuit.
Sheriff Paul Cruzier told them after the verdict: “You are acquitted, you are free to go.”
Patterson replied: “Thank you” before leaving the dock.