@law59 sorry your friend is going through this. I am 56 and also have this issue. Started to develop this in 2022, I have developed fluctuations in pain, ataxia and mobility. For me, rest up days before an outing. I try to gently stretch in bed bed before getting up, and anywhere before bed. The faster you learn to stop doing chores and such BEFORE you start tiring in the most important. Also, look into a rolator. They have a seat so you can sit when needed. They are not all the same, I suggest you rent one for a few days and take it shoping. You will lwarn alot. I was surprised when I rented one how inexpensive it is, and how simple things can inhibit independence. Examples, does it adjust enough to fit your proportions, is it to heavy or large, will the wheels work for the areas outdoors you want to go, do the cables catch on items when shopping, location of a basket, cane holder, backrest......
Ps, I was very active outside, city explorer, and love the arts. I am 5'9 120-125lbs and 56. Started having worsening issues shortly afterwards also. Read about pacing !