It's unbelievable that someone diagnosed with stage 4 lung cancer went almost year without seeing her oncologist regularly. Anyway... stage 4 lung cancer is terminal and pneumonia is a death sentence when combined with lung cancer.
I'd suggest you and your mother find God if you have not. Stage 4 lung cancer is terminal and it's a miracle she's alive after a year. If she has pneumonia then that will not help. I'm sorry to say this, but you should prepare for the worst. Be strong for your mom. Make every day count. But I do believe in miracles. I hope you get one