I've never lost patience with my grandma like that. She's old, a sweet person (most of the time) and perfectly intelligent if you let her be.
In fact when guiding her with tech, I hate the way she calls herself stupid and slow when she makes mistakes.
We just don't make tech for old people the way we should. There are "accessible" phones but the ones I've had experience with are atrocious hackjobs with deal-breaking quirks, when the whole point is to be simple.