I take long COVID very seriously - some of my friends still have long term issues. I don't think the post viral syndrome from flu is so common in the same age bucket.
However, her way is really unnecessary limiting, it is possible to take it seriously and enjoy life.
It is a pity you are asking in September, because starting opening up in June would be much easier.
We've just enjoyed the summer - eating outside and meeting friends in cafés' with outside seating. We visited summer cinema projections, we went for several openair concerts and festivals (not the kind when you stand in a dense crowd, the kind when you can place your own blanket and have a bit of space around you).
We like outdoor stuff in general, a walk in a nice area is great.
We visit museums and exhibitions (art, tech, ...) full year round - if the exhibition is open for months and everyone is buying tickets on the day, not many people would chose to go there sick. And if someone is, you don't have to stay in the same room with them.
We have FFP2 at hand when using public transport - especially in a high COVID season.
We pick holidays with an option of eating outside.
Not everyone has this options, but something from the list might work for them.
The goal isn't for them to forget about COVID no, the goal is for them to find a better balance.
And, I 'm not saying it is 100% infallible way, but it shifts the risks in a way we are comfortable with. And, we actually enjoy all those activities, so it works for us.