Sasha, I remember, not to long before your AXH died, you mentioned something about him either letting her drive, or that he was going to.. something along those lines.(?)... It could be that if he did start teaching her to drive, she is clinging on to that memory of him as one of the last "good" times with her dad. She may not want to override that which her dad may have taught her with what an instructor teaches.
Or it could be that she is a teenage girl, and they can just be pretty, shall we say, "challenging" even under the best of circumstances. I certainly struggled with my teenage daughter a lot more then I did with my son...And I know damn well I was not pleasant to my own mother when I was a teenager. I am sure your daughter grieving far harder than anyone her age should ever have to, is going to make your's and her situation that much rougher. Hang in there Mama.