Welcome rosie. What immediately comes to my mind are the "three C's" we talk about a lot in this forum:
* we didn't cause them to drink
*We can't control it
*We can't cure it
And if she is anything like my parents are as they hit their early 70's; they damn sure aren't listening to anyone else's criticism of their choices.
Is she hurting anyone else - bothering the neighbors, driving intoxicated, being inappropriate with the family in any way? If not, and she is just quietly living out her remaining years with alcohol as her crutch, then I am not sure you even have any kind of valid argument, short of the "health status" one.
I had a work scenario similar to yours, and here is how we handled it. The family hired personal care attendants to come in 3x a day, morning for an hour, lunch for an hour, and later dinner time for an hour. They were "hired" for mainly food prep and housekeeping, which the client was thrilled to have, but we all knew she was a heavy drinker, and they were there to monitor safety, as well. Make sure she ate, took her meds, had good daily hygiene, and hadn't burned the house down over night. It worked until she died, and she died doing what she wanted to do in her own house. To me, that was as dignified as we could make her life be.
So I guess my question back to you would be why do you feel obligated to point out someone's dirty laundry, especially if you have once and it was met with hostility? Wouldn't it be easier to work around this instead - doing the things you need to do to keep her safe instead of trying to force her into something she has made clear she is not ready to face?
I know this is hard...take good care!
~T