S.W.
Your MIL is going to "have to want to fight" the battle to succeed. She is also going to have to eat lots of nuts and dairy products to help with the radiation treatment. She may also get a metallic taste in the beginning but that does go away. If she believes in a higher being now is the time to get in touch with her inner self.
Treatments are usually for 6 to 8 weeks. The first part of the daily treatment is the basic treatment. The second part is the one or two weeks of deep down treatment. You will be advised not to miss any treatments as that will set you back in the scheduled routine. They may have built a body double for her to lay in in order to do the treatment depending on where the actual cancer tumors are located in her lung(s).
Know that she is giong to feel tired about two to three weeks into the treatment. Let her rest when she can and be positive.
I will keep you and your family in my thoughts for this holiday season and the future.
The other S.
PS I had cancer treatments 15 years ago. My drive to and from the doctor was about two hours each way and the treatment was all of about 10 minutes. During my drives I got in touch with my inner self and became at peace with my life and what was in it. Her priorites may change - what was important isn't and what wasn't is. Get her a journal to write in.