Chest CT-Covid or not. RT PCR result -ve

This is regarding my mother. Visited a pulmonologist with Chest CT Scan and various blood tests. Chest CT (please refer to copy attached) result said "multifocal patchy ground glass opacities seen diffusely in both lung parenchyma, more on the periphery and posterior location. Sub pleural bands seen in postero-basal segments of bilateral lower lobes. Moderate to severe infective etiology (most likely viral pneumonia)" Pulmonologist said this is corona, though I mentioned that RT-PCR test is NEGATIVE. He asked to admit the patient immediately. SPo2 is around 90-91 since 5 days. Slight fever of 97.5 in evening since 2 days. Breathless and coughing on walking. No coughing while on bed. Weakness is there. First symptom shown on 3rd August. Testing done on 10th August. No loss of smell and taste. Loss of appetite. Please see blood reports and CT attached below. Thinking of going for Antigen test tomorrow.Mother got wet in rain (slightly) on 1st august. First fever on 3rd Aug.