You siao ah. $4k is so low that if there was a poverty line in Singapore it would fall far below it. I earn 4.xk and I know how much of a struggle it is to survive. I would describe myself as living in severe and abject poverty as even young fresh grads now start from $4.8 to 6k (based on reading this forum).

Be that as it may, I wouldn't recommend TS to change job now because a place that will accommodate her health issues won't be easy to come by. Changing in the current covid environment also compounds the risk - people take big issue with any one that coughs and if TS is new to a company, chances are the people won't take kindly to her coughing. The finances of businesses are also less stable due to the covid recession.