Kirsten Coles, 22, lost control of the car during a blazing row about where her then-boyfriend, Christopher Ward, who left the Dolly Blues for a big money move to Birmingham City, had been until the early hours.
Police initially arrested Coles on suspicion of attempted murder but the charges were reduced to assault and driving without due care and attention as they could not prove the crash was deliberate.
Preston Magistrates Court heard that Coles had suspected Mr Ward of having cheated on her.
Coles punched Mr Ward in the face just minutes before the smash on Tom Benson Way, Preston, at approximately 3am on May 30.
Coles pleaded guilty to both charges when she appeared before Preston Magistrates.
Mr Ivan Dickinson, defending, said: "During the course of that evening there had been a number of calls between them. He was coming up with different versions of events about his movements that particular night."
Prosecutor Ms Catherine Ashcroft said: "She was driving – both were shouting and swearing at each other. Then Miss Coles punched Mr Ward in the face as she was driving."
The car went off the road, hitting the bank, before colliding with a lamppost and coming to rest in the middle of the road.
The couple escaped from the car and continued rowing.
Chairman of the bench, Christine Lomas, fined Coles £65 for assaulting Mr Ward and £100 for driving without due care and attention. She was ordered to pay £50 compensation. She was also banned from driving for six months.
Someone who knew the couple said Mr Ward had not cheated on Coles. He said: "He never got the chance because he was never out of her sight."