Determined Underachievers How to MOTIVATE a ringer who has reached a plateau and wishes to stay there, and becomes stressed when I guide her towards the next ascent? — Barbara Le Gallez
You are right, it is about motivation. Maybe there are clues in the language used to pose the question. Should we be using mountaineering analogies in the first place, since most people do not aspire to climb mountains?
Even if we do, a plateau is a good place to be, because it's easy to move around with little effort and there are good views to all around laid out below you. Also, you cannot go up from a plateau, it is a flat top.
I think the concept in your mind is a ledge, a level part of an ascent where you can rest ahead of the next climb. I don't think that is how most people think about ringing, even the ones who want to progress (and the ledges I've sat during climbs were not places you would want to hang around anyway).
You said she just wanted to 'have fun'*, ie to enjoy her ringing. That's fine. It's possible to enjoy doing familiar things and it's possible to enjoy playing round with novel things, including laughing about it when you get it wrong. It all depends on what mood you are in.
In the right mood, trying something new, messing up a bit, maybe succeeding a bit and maybe learning a bit in the process can be fun, and even fodder for yarns in the pub. But in the wrong mood it won't.
Harking back to my hang gliding days my instructor said he would never tell me when to fly, I had to decide that for myself. On that occasion I didn't, but if I had done I would have been in a very different frame of mind if I had decided, rather than having to go because it was my turn.
Not sure whether any of this will help, but you never know.