Hello and Congratulations to your mom on her recovery. This issue that she is having with regard to incessant coughing is a very common sequelae among patients recovering from Covid 19,because of the residual lung damage that's left behind,which will clear out with time. Hence don't panic . Assuming what you have said is correct and she doesn't have any other symptoms like Fever. It's probably a harmless issue which can be controlled by simple medications. Please enroll in a proper Post Covid Follow Up program,where repeat investigations are mandated,given the fact that in the Post Covid period the body is very susceptible to catch infections,more so in case of your mother,cause of her age.

For cough you can do warm water saline gargles 3-4 times a day, drink luke warm water, and take syrup Adusol 2 tsp 3 to 4 times a day with warm water. This will take care of ur complaint.