Welcome to our very exclusive club. It is unlike any other, because we are, too, unlike the average person.
Everything about ALS is bad news. It's hard work for the CALS, and harder for the PALS.
I'll give you my experience. Others may have different experiences.
She might live 8 months or 8 years. There's no way to tell in advance.
Doctors will tell you the standard party line: 3-5 years. But I wanted a more nuanced opinion, so whenever my PALS had already left the Dr's office, I would excuse myself, go back to the doc, close the door, and say: "I have to make plans for the family. I'm going to build a new house to accommodate my PALS that will cost a half-million. I'm thinking of moving my kids to a different school and arranging for private daily transportation for them. Tell me, doc, what do you really think?"
The doc shook his head and quietly said, "She won't last the year." With that, I could care for her better, I could budget the money better, etc.
Life can be good. Some PALS ski. Some travel. In her wheelchair, we took my wife out to eat, we went to parties, we saw the kids' soccer games. The American Legion even presented her with a medal during the awards ceremony in the middle school gym.
Hope. PALS need hope like anyone else. Since they can't reasonably expect a cure or even a long life, I made sure my PALS could at least look forward to a happy life in her months remaining. Plus, I assured her that our kids would be happy and secure on their way to college.
I made it my mission in life, all day every day, to anticipate her needs and prevent problems, big or small. I got A LOT of advice by reading this forum.
Important: Is she a veteran of military active duty? Makes a difference.
One big, hairy decision she'll need to make is about tubes. Feeding tube and breathing tube. There are many pros and cons. One of the effects is that tubes can keep her alive longer. But that life might be paralyzed in a bed staring at the ceiling for years, unable to communicate, waiting for a family member to pull the plug.
Some PALS have told me that, although they were completely paralyzed, they still had a quality of life and wanted to continue to live. I can't imagine that for myself, but I believe them and support them.
My wife decided against tubes. No feeding. No saline drip. No trach. She would have lived longer, perhaps, if she had tubes. But she didn't want to live like that. She ordered, in writing, that if she ever couldn't breathe and needed air, we were to give her morphine instead. (The morphine would eliminate the panic one feels when you're lacking oxygen.) She lasted 9 months from first symptom to totally locked in, unable to even blink to say yes or no. She was in that condition for just one day before she passed. During that day, she was pretty highly medicated, so I don't think she felt scared about it at all.
Everybody makes their own decision.
Someone needs to wipe her bottom. Someone needs to scratch her itches. She'll need frequent leg massages to relieve the pain of immobility.
Friends and family don't know how to handle it, and feel uncomfortable. Many will just disappear. She might need a van with a ramp and someone to drive her.
It's hard, expensive, sleepless. And at the end, she's gone. My advice here is this. We know that ALS will destroy one life, all you can do is ensure it doesn't destroy two lives. So be sure to plan for a future life for the survivors, too.
My biggest advice is to help the PALS get her wishes. That's the best thing you can do for her, I think. What she wants, she gets. I never tried to talk her out of anything. Even if you know better than her, even if you think she's wrong or "just being emotional" I would smile, say yes, and do my best to follow her desires.
That's hard advice to follow. But, however, put yourself in her place. If I were dying and I wanted something or made some decision, and then someone else over-ruled me, tried to disagree or used my helplessness to counteract my decision. I would be LIVID. If I'm the one dying, then I get my way, period. That's my advice. Some will disagree.
Frankly, ALS is not your problem. It's hers. You could just leave her. It's her problem and you're not married to her. If that's your decision, I personally ask that you be honest about it with her, and help her make other arrangements for her care with her parents or others. My PALS lived her final months in our living room in a hospital bed, so that all the family would be near her all day. We positioned the bed so she could see and operate the TV and speak easily with us all. I put all the "hospital equipment" right behind her where she couldn't see it but it was ready for any emergency. I bought a generator and a window air conditioner in case the power went out. I slept next to her in a cot, touching her, whenever I could catch a nap.
We in this forum have been through this many times, and we know the solutions to many problems. Sometimes there are no solutions in ALS. Don't be afraid to ask.