I made sure to disable every unneeded interaction she might accidentally stumble upon:

1. Volume is set to maximum and volume buttons disabled so she won't accidentally mute it
2. All assistant and other unnecessary shortcuts have been disabled
3. Removed all quick settings that actually do anything and only left ones that either open apps or just don't do anything (eg Cast since she doesn't own a smart TV)
4. Locked the home screen so she can't accidentally move any icons
And more