I am so sorry Linda. ((((((((((((((((Hugs)))))))))))))))). When my Dad went through lung cancer, he initially chose chemo, even though they said it may only extend his life 6 months at the most. At that point, he felt like he needed to at least try something and was not willing to "quit" yet. This is how he viewed it and it is a very personal decision and one that only your sister can make knowing she has the full love and support of her wonderful sister and family in whatever her choices. For my Dad, the chemo did not help. It only made his last few months that much more painful and I wish he would not have suffered like that, but, it made him feel that he went down fighting and that's what he needed.
You and your sister are in my thoughts.
2001 Trek 7500 FX, converted to a hauler - Serfas
200? Marin hybrid - Selle San Marco
2004 Trek 5200 - Avatar
2011 Trek 6.2 Madone - Ruby