I'm sorry
but other than supervising her, which I would assume is already required for her age, let her be. At 80 she would be likely to fall at some point sober, without supervision. The alcohol probably saved her from breaking a hip. If drinking makes the pain of living tolerable be grateful she has something that works.
"I doubt that she has many years ahead of her. Emotionally, she's been ready to die for years. If someone told her she was drinking herself to death, she'd think that was fine."
Why take away the one thing that seems to make her comfortable?
Edit to add: This is just my opinion - how I would wish to be treated if I found myself in her situation.
Kick in to the DU tip jar?
This week we're running a special pop-up mini fund drive. From Monday through Friday we're going ad-free for all registered members, and we're asking you to kick in to the DU tip jar to support the site and keep us financially healthy.
As a bonus, making a contribution will allow you to leave kudos for another DU member, and at the end of the week we'll recognize the DUers who you think make this community great.