I think she is deficient in Vitamin D3. I suffered for decades every winter & spring with a TERRIBLE chest cold that started in my nose, spread to my throat and then into my chest. I sometimes even lost my voice. I also caught every flu that came around.
Then I discovered Vitamin D3 and I haven't had a chest cold or the flu in 8 years! Now the worst I see are a few sniffles during the winter. You need to take enough D3 to raise your blood test to 70 - 80 ng/ml. For most people this requires 8,000 to 10,000 IU D3 oil based Geltabs. Some people may need co-supplements if they have trouble raising their blood level.