Hello
I understand your concern.
Persisten cough,runny nose,
fatigue beyond 3 weeks can be because of
chronic sinusitis causing post nasal drip/pneumonia secondary lung complications/secondary
atypical pneumonia.
If I were your treating doctor,I recommend,
-Steam inhalation using mucinex capsule 2times a day
-
Nasal irrigation with saline
-Avoiding exposure to secondary smoke or environmental air pollutants
-Maintain plenty intake of water, healthy diet,breathing exercises for general well being.
-Certain investigation will be required.
CT scan chest for pneumonia complications and atypical pneumonia.
Nasal swab and bronchial swab culture and drug sensitivity.These tests will help to know the causative organism and also the effective antibiotic against it.
Nasal
endoscopy by ENT surgeon will be required to find out underlying cause of chronic sinusitis like nasal polyp.
Hope this information helps.
Wish her speedy recovery.