I don't think pissing her off is a good idea right now.
Weather you paid for it or not, with it in her name, and in her possession, she can do what ever she wants with it. That would include selling it.
Now I don't know the situation, but my guess is that with it in her name he can drive it with no license and can get it back when it is impounded. If he is pulled over alone, with no license, the car is impounded. A lot of tow companies won't let the car go to anyone but the owner and you can only leave the premises if you have a license.
Being in her name would allow the car to be picked up by her after an impound.
Like I said, I don't know the situation and that is my best guess by what I have experienced. My ex in high school, her dad owned one of the biggest tow companies in the area. I heard about that situation more than a few times. It is sickening how many people drive around with suspended or no licenses.