another question about Tagrisso not working and alternatives

Hi, this is my first time finding your site. Huge thank you to all who have made such an amazing resource available. In January of last year, my SIL was 63 when she was diagnosed, out of the blue, with stage IV lung cancer--which had spread to both lungs, liver, bones and the fluid (??) around the lungs (Not sure about that). She has EGFR mutation and so started Tagrisso and everything went fabulous. Great PET scan in January, but now, four months later, her CT scan shows very small lung and liver spots that weren't there before. No change in her major large tumor in her lung (that had shrunk considerably), nothing new in her bones. She also has had some minor fluid buildup around her heart but the cardiologist says its fine. After this result, she sees her oncologist on Wed and the nurse already warned her that she will be recommending immunotherapy and chemotherapy. My sister in law is quite fragile and she is very sure that the side effects from chemo would be more than she could bare. Even with tagrisso she has struggled with stomach issues. I am wondering if anyone can give any insight into how likely this new combination will give her some good quality of life going forward or if she will be very sick and feel awful during this treatment. She lives alone, will that be possible? Also wondering if staying on Tagrisso makes any sense. I saw some posts from a few years ago that some are staying on Tagrisso and using radiation for the new mets. Perhaps this is old thinking now?? Any feedback or thoughts would be super appreciated. Thanks in advance.