What food sources would you recommend?
If you want to follow a more formal diet that attempts to minimize autoimmune issues, there is one from a Paleo perspective, and others from a vegan perspective. Information on the Paleo one is here:
https://draxe.com/nutrition/aip-diet/
https://drjockers.com/autoimmune-diet/
However, if one knows they are truly not allergic to certain foods other might be, the approach is simpler. Simple sugars and Omega-6 fats are pro-inflammatory. Don’t use them, and stay away from breads and pasta, too. Increase your intake of high antioxidant foods. Look into supplements to further tweak your body’s immune system.
A few links:
https://www.livestrong.com/article/263431-the-best-vitamins-for-autoimmune-problems/
https://www.liverdoctor.com/the-importance-of-glutathione-for-autoimmune-disease/
Hope these help direct you and your wife!