Ugh. I remember having this same argument with my DD and she was not grieving, but she sure stuck to not wanting those lessons. I stayed very matter of fact about it and just said well, there is nothing to talk about and if you want to drive this is what will happen. Eventually she just gave in and it was fine.
I am sorry. Who knows what is in their minds, or like you said, who knows what he said to her. Ultimately, she seems to have a good head on her shoulders and will come around.
Keep with it tired momma. I hope in all of this you are able to make some time for you and taking care of yourself too!
Huge hugs!