Can you give a ballpark prognosis of a woman in this condition?

I have an old friend , my ex’s girlfriend, who at age 59 is not overweight but after smoking most of her life often carries around an oxygen tank. I’m not sure “prognosis” is the correct term but do you think she could have a long life ahead of her, there is no way of knowing or do you think she’s in deep trouble physically? I mean, is this a serious condition? Or can you live another twenty years+ on oxygen if you began using it at age 56?