I’m actually reading this in a different way than you interpreted it- I see it as religion can be a coping mechanism, like many religious people feel like your grandma “I’d be so scared without religion” because they use it as a reassurance that everything will be okay, that there’s a reason for everything and that God has a plan for you regardless of how you’re feeling right now
I’m not religious either, probably because I have the “everything will be okay” mindset without needing religion for it, but I don’t see what she said as a negative thing or as a “pray it away” thing, more as a “I can’t believe you can cope with something like this without believing in god”- obvs I don’t know you or your grandma, but this is how I interpret it