Well, I offered to switch back, explaining to her that I made the change in order to make it more difficult for her to meet with her boyfriend. She refused, saying "the wheels are in motion" (whatever that means).
My next step is to call her father and tell him I offered her the car, and she refused to switch back. I will tell him that there is a reason that she needs his help: Because we cannot afford a new car. I will also explain to him the reasons that I made the change.