I too felt sorry for my mum, on reflection my post earlier made me sound like a uncaring pratt and my mother a very gnarly and stubborn thing!
She was very stubborn, set in her own ways, she still lived in Victorian times in her head!
But stubbornness is enemy number one to an older woman, and you cannot change anyone else's outlook!...sad, sad, sad.
But you have your own life to live, your own family to think about, and its your mother not your wifes!...and that too causes issues, I know that first hand.
Good luck mate!
Cheers King Billy