Grandma is probably going to get onboarded onto nostr by her family, using some very simplified client. Her WoT will be bootstrapped by her family members and she'll probably use a WoT service provider that automatically gets configured for her via the fact that her grandson referred her. She won't know about any of this, just like she's not exactly sure how her iPhone address book has her family in it... and occasionally she can remember how to add the electrician or a new friend when the stakes are high enough.

Her WoT will be extraordinarily family-centric and will remain that way as long as she doesn't explore too far outside the bounds. If she does, she'll start to develop her own parts of her own network. Maybe one day she'll be installing new weird clients and vibecoding applications and custom NIPs - but probably not. WoT would be invisible guardrails for the first half of that interaction pattern, but is entirely malleable by the user if they demonstrate the competence (via their usage of various clients) to discover and push against the railing to go deeper into that second half.