Her friend probably thought, "hey I also sometimes feel a lack of spoons". But the enormous extent the author has to deal with spoon management still surprised her friend. It surprised me too.
I don't think it's ok to have such a lack of spoons. I think some people are indeed very lonely when it comes to their kind of lack of spoons. I don't think thinking that way is harmful. Getting such a severe illness is a severe loss of life quality. You will probably grief for the rest of your life. It's nothing you can fully move on from.
At least I would never hug a person with such a background while saying "I understand you". That is impossible for me. Hugging, of course, yes, but claiming any real knowledge about how such constant lack of spoons must feel is impossible for me.
That is just acknowledging individuality and diversity. I will still demand stuff from those I cannot understand well. For example abiding to laws etc. Individuality does not automatically imply immunity to judgement or special treatment. You seem to think that.