I recently visited my 86 year old aunt who although she has all her marbles, has very bad osteoarthritis and is mostly housebound, she is not overweight. On mentioning that I have Type 2, said that she had been told by the nurse that she was diabetic, but that she didn't need to do anything about it.
She is on the eye screening programme, so must have been diagnosed. She is quite stuck in her ways, so I can't imagine she would easily take to dietary changes. I'm sure her GP is quite happy to take the extra money for having a diabetic on his list.
I was diagnosed at 47, so hopefully I have some years to live with this, but at 86 she has outlived all her siblings who died in their 50's/60's/70's, so I'm with the nurse on this one, let her carry on the way she has been eating, the nurse would probably tell her that she needed to eat starchy carbs with every meal anyway.