Su Zhiruan wasn't wrong; as soon as she got in the car, she started recording.
Based on the original plot and her experience, Ning Fu's greatest skill was blatantly lying, presenting one face in public and another in private, and being adept at distorting right and wrong.
When she heard Ning Fu take the initiative to offer her a ride to the college entrance examination venue, Su Zhiruan immediately sensed something was off and quickly started the recording.
Indeed, in modern society, sound recordings are the most effective tool. Just throw out a recording when you're being slandered, and everyone will fall in line.
After all, hard evidence is incontrovertible; she couldn't possibly be editing Ning Fu's words on the spot.