The messages "Cheater," "Hope she was worth it," and "It's over" are visible in photos of the vehicle posted to Twitter by user @kloidaaa.
The Twitter user said she saw the woman spray-painting the car, but didn't snap any pictures until the deed was done.
"I have no idea who she was -- she was just going crazy," she told the BBC. "No one tried to stop her. She just left afterwards."