Interstitial lung disease a chronic progressive disorder and generally of autoimmune aetiology. Generally patients require systemic steroids and steroids are double edged sword as they benefit but in long run may produce many adverse effects on the body like Osteoporosis, Thinning of skin,decreased immunity and hence your mother had reactivation of Herpes virus due to immunocompromised status due to intake of long term steroids.
Due get her Interstitial disease evaluated, try to give her lowest possible drug dosage which stabilizes her lung disease. She can also take steroid inhalers where the drug is effectively delivered at the diseased site with very little systemic absorption which is primarily responsible for adverse side effects.
Also patients on long term steroids should take appropriate intake of Calcium, Bisphosphonates to strengthen bones,Proton pump inhibitors to prevent acidity etc.

1. Interstitial Pneumonia is the most common pattern of Interstitial Lung disease (ILD), resulting in scarring of both the lungs, and ultimately inflammation and fibrosis. Any systematic symptoms (shortness of breath,cough) noticed by your health care provider??
2. any associated Auto immune disorder like RA, lupus, scleroderma??
3. Since it's an Inflammatory disorder, thus cortico steroids are given to reduce the inflammation, thus in your mother's case, prolonged use of steroids and complications of ILD has resulted in Hypertension, Weight loss., check with bone mineral density (BMD) for Osteoporosis
4. moreover steroids causes Immuno supression, thus herpes infection has occurred due to lowered Immunity against secondary Infection.
5. main complication of ILD is scarrring,which can't be reversed, so Pulmonary rehabilitation is treatment of choice:
i. breathing techniques to improve lung efficacy.
ii. emotional and nutritional support.
iii. oxygen therapy along with yearly influenza vaccination and periodical pneumococcal vaccination.