First of all, if you believe in prayer, pray that she be in as less pain as possible while she's going through this. Then spend as much time with her and her husband as possible. When she doesn't feel well, make time to spend with her husband. He'll need to be there with his wife a lot, so maybe one of you could stay with her and watch a movie or play a game while the other takes him out and does something he really enjoys doing. If he wants to talk about it, just be a good listener. You don't have to say much, just let him do the talking. He's going to be hurting a lot. He may even be grumpy towards you at times, but try to understand he's about to lose his life mate. Just support both of them in the best way you can. And when she's gone, try to make sure he doesn't close up like a turtle and just want to forget life. He'll need to mourn for sure, but try to make him realize there's a reason he's still here. People still love and need him. I'll be praying for him and his wife. I'm sorry for you, too.
If you believe in God a prayer for all may help. Just making ones self available is really all that can be done. It stinks, it's not fair, I hate it, I've been through it, I know I'll go through it again & it will still stink, still be unfair, piss me off , & will probably happen again. Hang on to each other, love each other, & no matter what be strong for them. It's hard enough & painful enough for the 1 about to die, do not add to their pain but showing yours
Im so sorry to hear about your situation. Cancer is a terrible thing. Sometimes doctors can be wrong who knows how long she will live. Its a hard thing to realize but it may be better if she was not suffering. You need to live in the present and take advantage of the time you have left with her. Do once in a lifetime things and your love. miracles do take place whether your religious or not. maybe they will find a cure for cancer and she will be cured. also offer to help them out with housework or anything else. most of all be there for them sometimes a hug really helps. Good luck i wish you and anyone else in this situation the best.
My best advice is don't ask questions, like what can I do? do you need anything? Thats what everyone says, its exhausting and the answer is usually nothing. Be there. Bring happy memories. Make these last months count. It's sad but save your grieving for the end. My heart goes out to you.