I'm so sorry to hear of your mother's sinus issues.
If the problem stems from medications, a natural remedy that I have been recently using is halotherapy. I visit a salt chamber multiple times a week. It has not cured my sinus problems, but I sleep and feel better afterwards and it does help with feeling less blocked in my sinus. I have taken so many medications for my sinus issues which have not worked, I am now resorting to alternate therapies. The facility I go to offers a monthly pass with unlimited visits. I was told after 10 or 20 visits you really notice a difference. I have been maybe 6 times so far. If you cannot take her to a salt chamber facility/spa that offers this service, there are medical Himalayan salt devices on Amazon that may give some relief if you are interested in trying alternate options. I can't say whether it is the placebo effect or if it works, but one theory is that anything that makes your body stop and relax and do nothing but breathe for 30 - 45 minutes can only be therapeutic. PS the most effective sinus medication I have tried is MUCINEX DM. This has been more effective than prescription medication in my personal experience. As for the halotherapy, its natural and can't do any harm, I am hoping it will soon fix my problems.