Check the medications, as some of them also can cause damage to the lungs (f.ex metotrexate), so always read the things, ask a pharmacist and discuss it with the doctor.
Very good she had symptom relief when taking D-vits! :) If taking NSAIDs, get the iron levels checked regulary, as it can inhibit the uptake of iron.
Pulmonary manifestation of rheumatoid arthritis include various forms of interstitial lung disease/fibrosis, bronchiectasis, necrobiotic sometimes cavitating nodules, and/or pleural effusion/thickening.
Sorry so late - I just saw this. It does appear that RA is linked to lung scarring: https://www.mayoclinic.org/diseases-conditions/rheumatoid-arthritis/expert-answers/rheumatoid-arthritis/faq-20058245
There's no one "tablet" that people with RA would be taking, so you should definitely discuss this with her doctor.