I'd be curious to know the reqson why she would care on her own phone and why it would be an issue on someone else's phone?
Despite this, many of my relatives have somehow learned this habit of opening the switcher and closing all apps when they are done with them.
That being said, I dislike having 3 dozen apps open because I simply can’t quickly find and switch to the ones I’m using. So when I enter a new situation, I swipe all the way left, and Clear All apps, to start over with a tabula rasa.
But the switcher shows every app ever opened and tries to pretend these apps aren't being closed. Right now for instance, i just checked and as best i can tell, the last 3 were open. going back any further and i could tell the app had to reload. but i can scroll to the left back forever. the one on the furthest left i easily haven't opened for months