it's a tough one to call as it is often mixed into the same symptoms as Lyme and some others like vitamin B-12 deficiency etc.
Fibromyalgia is often treated with steroids,... Lyme with antibiotics. Two different schools of thought.
After months of meds I found that if i rested and did not hike or exercise I would hurt...even if just lying in bed.
So I reasoned that since I hurt anyway I might just as well do some activities like a daily walk for example.
Sure enough as the weeks went by I hurt less and less. Now I can go out for a 5 mile walk no problem (that is up from the 600ft I could barely do a couple of years ago).
So while I don't know the answer for your friend, I find that now I take no meds but a fair amount herbal supplements and go the diet and exercise routine with good results.
In one manner of speaking I could say that the exercise made me more pain free....but more realistically I did most everything I could possibly think of, to get better.
There are so many variables I did all I could possibly do to improve my situation even if it meant disagreeing with one doctor and moving onto another and another till finally finding my way through it.
If Fibromyalgia and some of the other illnesses that are often lumped together categorically as a generic "what the heck do we do with theses people"
It's hard to say the exercise itself will lessen the pain...I think it's more of a whole all encompassing effort to fight it....it changes ones approach to life and the will to get better is extremely motivational... to not fight is a battle half lost already.
Wishing the best for your friend.