M.D.
First let me say that I am so sorry you are going thru this. My dad was diagnosed with stage 4 lung cancer in Jan of 2009 and he passed away in Dec 2009. So, I totally feel your pain! Yes, you need to respect her decisions and enjoy the time you have left with her. She is the one fighting this battle and I believe that people know when they have had enough. It is a hard and very exhausting process- for the family and especially for the one fighting.
My dad tried 2 types of chemo which did nothing but drain him of every ounce of energy he had. He told us "he would not be a guinea pig to many different types of chemo. If it didnt work, then that is how it is meant to be." His last type to try was Tarceva- it is a daily pill, yes its chemo just in a different form. (VERY EXPENSIVE) It worked for a short time and gave him 4 great months to do whatever he wanted. He went from sitting in his chair 95% of the day to running errands, playing golf and going to a 5 day camp/cook out that he had been planning for a year. It was an amazing 4 months. Then in November things changed almost suddenly- it just quit working on him. He knew it was time and he passed away a week before Christmas.
Sorry for rambling. Your mom and your family is at a point that it is about quality of life, not quantity. You want them to be around for years longer but not if it means pain and suffering for them. Enjoy the time you have with her.. it passes so quickly. I miss my dad everyday and there are so many things I wish I had said and done. I always thought I had one more day. That is one piece of advice I can give you.... Dont EVER think "oh I will tell her tomorrow or I will take care of it later." My dad moved to hospice awake and coherent. It was late that evening when they moved him and my sister and I decided to let him get settled in and go visit the next day. He was never awake again after that night. The next day when we got there he was alive but not awake- he passed that evening. It went so quick- the doctors thought we had another week. I will always regret the decision I made that day. But I know he was tired of fighting it and ready to go on. Good luck to your mom and your family. I am very sorry.
If you want someone to talk to- feel free to PM me.