Thanks for those cites Karl. If the symptoms go away with the cessation of her soy intake, I guess we’ll be safe to assume she is one of those 20% (for now).
My first thought was thyroid issues.
I’ve had these symptoms since puberty (ten years old or so) but the TSH came back as low (borderline) for the first time when I was in college. Get it tested again… and I would suggest synthroid again but IANAD. It helps that synthroid is cheap, so if her doc does prescribe it and it’s not for her, she’s not out hundreds of dollars (thank you, Celebrex) 
It’s amazing how many problems can be solved by my tiny dosage of synthroid.
Also, have the lab check the blood sample for anemia.
Here’s an odd question. Can thyroid problems be mistakenmisdiagnosed for rheumathoid arthritis?
Well, thyroid problems and rheumatoid arthritis tend to occur in the same individuals. People with RA are more likely to develop thyroid disease and vice versa.
RA has a pretty predictable set of features which, I suppose, very early on might resemble hypothyroidism (fatigue, aches and pains, anemia, etc). And, sometimes hypothyroidism promotes other types of arthritis (i.e. pseudogout).
Still, the two conditions are really quite distinct.