I'm trying the same with my mum (70 years, severe COPD, but still smoking...).
The way I do it now, is by not forcing her into anything, however I am making sure her current vaping supply is up to date.
Also, I make sure I have something new to taste when I get there, and vape around her all the time.
It is working ; while she initially only wanted small thin ecigs, she's recently requested me to get a bigger battery for her, and yesterday she received the Ego Twist. Next stop, Provari?

We're getting there, but she herself determines the pace. Eventually she'll make the switch ; she already went down from 10 cigs a day to 2, and replaced the other 8 by vaping.
That alone already is very positive.