Wife refuses to use two hands

Like the title implies, my wife refuses to use two hands even though I told her the feel and stroke she will get will be far superior to a one hand stroke.

She has always struggled with her back hand, always resorting back to a one hand stroke. Any tips out there to get your wife and/or partner to move to two hands?

I use two hands and it has changed the game, my strokes are short and concise and alway result in a massive finish.