I had suspected SLE 4-5 years ago (doctors couldn't confirm it because the tests weren't conclusive but had all symptoms and blood tests pointed towards it - so frustrating not to really know) and I was desperate to avoid the life of drugs that I was destined for. My rheumatologist gave me 2 weeks to see if I could fix it by diet but didn't (and still doesn't) believe that diet could affect it. Well, within a week of commencing an elimination diet my pain and fatigue was almost gone. I could not believe it myself. Blood tests showed that inflammation in my blood had dropped dramatically to almost normal. Unfortunately, I'm not completely sure what the cure was but I can tell you that out of the food I eliminated, the only ones I have never gone back to are coffee and aspartame (and I have since read horror stories on that).
At times, I still get some slight joint pains, and it seems exacerbated by stress, but I don't need to take any drugs and compared to what I was a few years ago I feel on top of the world.
Before low carbing I also experienced periods of severe lethargy but since this WOE I have gained a lot more energy and no longer lethargic. I go to the gym 3 times a week and aqua twice a week - something I could never have done before.
I take a good multivitamin, along with 4grams a day of Omega 3 fish oil, vitamin C, acidophilus, among a few others my naturopath has prescribed for me.
So, after all that, I think your wife should go for it. It has certainly not harmed me, in fact I feel better for it. What can be wrong with eating lots of fresh food with no refined white flour and sugar. Perhaps she could include some oats and whole grain bread as some low carb diets do (I have an allergy to wheat so I avoid it). If I had listened to my doctor, I would be on drugs, and probably living a less full life.
Melberry