As I thought about it, I remembered noticing some irregularities from the time Nadia became ill until she passed away.
I recollected that before Nadia fell ill, Mona had brought Nathaniel to our home, and they had caused trouble for quite some time. They refused to leave even after we offered them money and ended up staying for over two weeks.
During the two weeks that they stayed in our house, I noticed that Mona's behavior was peculiar. She took it upon herself to cook for Nadia and even brought some herbal tonics from her hometown, claiming that Nadia was too thin, and cooked them for her.
If I wasn't mistaken, Nadia had fallen ill shortly after Mona and Nathaniel left our house. After being taken to the hospital for a check, the doctor diagnosed her with acute pneumonia, likely due to inflammation and prolonged coughing.
Nadia's cough started after she drank Mona's herbal tonics. I even inquired Mona about it.