Oxygen saturation does not necessarily predict how long one will live. There are people with longstanding lung disease who live for years with oxygen saturations of high 70 s low 80 s. What is perhaps more predictive is the work of breathing the elderly lady is experiencing. If her breathing is fast, then a she may tire within even a few hours and pass away from respiratory failure. To maximize her comfort, I would recommend giving high flow oxygen through a face mask with a reservoir bag. Obviously treatment of the urinary infection and proper fluids and nutrition are also critical. If she does get worse, there is no place in a case like this for intubation or invasive resuscitation. I wish her a speedy recovery, which is still possible despite her current condition.