Hi, welcome to LCSC. I'm very sorry to hear about your mother's illness — she sounds like a real trooper! As an ex-military person myself, I have a huge respect for the ladies who led the way in "degenderizing" (I thought I was coining a word, but now see it's in the dictionary!) our armed forces back in the 1940s and thereabouts. Please give her a nice arm-squeeze for me.
Her doctors' hesitation in giving chemo to a 90-year-old patient is well founded. For someone in a debilitated condition, chemo is far more likely to do harm than good, and that's true for younger patients as well. But if she recovers enough to get around without much difficulty, they might be willing to try one of the less challenging treatment options.
The docs say that the sides from the chemo are horrible.
Not necessarily. Do you know the subtype of her lung cancer? More options are available if it's adenocarcinoma, and one of the gentler chemos effective for that subtype is Alimta. Another possibility is a daily pill, Tarceva. I've seen both of these recommended for patients over 80.
May I suggest that you visit cancergrace.org
(GRACE — Global Resource for Advancing Cancer Education). GRACE is led by Dr. Howard "Jack" West, a Seattle oncologist who is an internationally-recognized expert on lung cancer and who gives high priority to promptly answering questions online. A lot of us are "dual citizens" and have the same usernames there as here.
Best wishes and Aloha,