Kellie,
I too was a smoker, but quit almost twenty years before Dx.
I was also a "tough guy" who didn't want to take the pain meds. Afraid of addiction and losing control. Neither of those were an issue. I continued to resist until a caring nurse at the Univ. of Chicago said to me " Your cancer won't go away any faster by your being in pain, but your recovery will be faster" I then gave in and let them adjust the pain meds to appropriate levels. I got up as high as the 100mcg Duragesic patch, and used the morphine sulphate to address breakthrough pain ussually before meal times. I never had a feeding tube, and was able to take my fluids orally. I was never "buzzed" on the meds, and in fact maintained enough motor skils to do pretty well on video games.
It really is important to get the pain under control and as many have said already, the most significant pain was during the six to eight weeks after the last radiation treatment. Hang in there with her. Your support is important. It may sometimes be frustrating, but believe me the support from my family was an enormous help in my recovery. Keep coming back here. You can count on the people here to give you and your sister support you'll both need.

Chuck