Hello dear I have gone through your query and understood your concern. A healthy immune system often successfully fights TB bacteria, but your body can t mount an effective defense if your resistance is low. Diabetes ,especially uncontrolled diabetes can weaken the immune system.Thi is the reason why your mother s immune system could not prevent her from becoming sick. He is hospitalised and with her actual condition i m sure that her doctors gave her insulin therapy.This therapy is absolutely necessary for her in this moment. About the diabetes diet my advice for your mother is to eat healthy foods in moderate amounts and sticking to regular mealtimes.This helps her body better use the insulin it produces or gets through a medication A diabetes diet is a healthy-eating plan that s naturally rich in nutrients and low in fat and calories. Key elements are fruits, vegetables and whole grains and avoid procesed foods and saturated fats. Anyway this advices are for the time when she will return back home because now she is in hospital and i m sure that she have the right diet and treatement for the moment. Hope this information is helpful for you. If you have other questions,feel free to ask.I will be happy to help. Take care.