Wow, that is very good news for people. I had no idea being in that bad of shape could end up with such good results.
I have been on this site asking questions because my sister is the one who had exactly the same thing going on 5 yrs. ago. She was at death's door - just like your MIL, with the same diagnosis. She was 54 yrs. old at the time. A little younger than you MIL. My sister started drinking when she was 14 yrs. old and never had a sober day. Her liver finally gave out 40 yrs. later and the doctors told her that if she had one more drink, she would die. She spent 10 days in the hospital, and had numerous blood transfusions, had to have so much ascites drained from her abdomen and legs. (Her friend said she looked like she was 12 months pregnant with triplets.) She was full of jaundice and varices in her esophogus, vagina and colon. (She had so much blood coming out of her vagina, she thought she had her menstrual cycle again.). After 10 days in the hospital, she was sent home with a new diet. She went on a low-salt, low protein diet and had no alcohol. This was 5 yrs. ago, and she is still here. I am not sure how she is doing, as she lives 1500 miles away, but she sounds good on the phone. She has had some kidney problems, and maybe some other liver related problems, as she is now on a no-salt diet, and is on different medications to help with fluid build-up. My sister decided she wanted to live and from what I can gather, she has done a pretty good job building her body back from death's door. So - 5 yrs. later, this is her story. I don't know why she made it this far, other than she listened to her doctors, and goes for regular blood work and check-ups as needed. As stated from others more experienced, each person is different and each person has a different will to live. I wish your family the best in this journey.
Evening
Her age is against her making a recovery, im sorry to tell you she is in a very dangerous situation right now that could results in her death at any minute. Acute Alcoholic hepatitis kills 50% of people in a month on its own even without cirrhosis. Sorry if this post sound negative but you have asked for the truth, I dont what to give you false hope either.
All hope is not lost however, if the Alcoholic Hepatitis subsides she may be able to get some Liver function back, but she will still have the Cirrhosis which progresses anyway, she could get another 1-5 years but only if things go very well from here on, which is not that likely given the symptoms you have described.
Just incase you want to know, Cirrhosis is scarring of the Liver and Hepatitis is swelling of the Liver. Acute swelling of the Liver can be fatal and Cirrhosis will also be fatal, this is where the Livers cells are replaced by useless scar tissue, its is caused by Hepatitis over usually a long time. Your mother in laws problems are likely to have started years ago, she just didn't feel anything because the Liver doesn't have nerves to cause pain.
I pray something good will happen here, but you may need to prepare yourselves for bad news.
This is more a question about alcoholism and it long term consequences but I will tell you the realities from a medical, liver disease perspective.
I am sorry to hear of your mother advanced liver disease, addiction and her poor health status as a result of her alcoholism.
Unfortunately only your mother can determine what will happen from here. Only she can decide to save her own life or continue on her path to a bad outcome. If she continues to drink her liver disease will continue to get worse and in time the resulting liver disease will be fatal. As the doctors told her, with her continued drinking, she is not eligible for a liver transplant which is the only treatment option for anyone with advanced irreversible cirrhosis.
So unless your mother changes her ways soon am afraid there is little to no hope of her recovering her health.
As to how long someone in her condition will survive...it is unpredictable. Everyone is different because each persons body can handle different amounts of disease. So can survive for a long time and other can have a quick decline literately over night.
I am sorry that you have to good through this. My best wishes to you and your family who are dealing with such a very sad situation.
Hector