I don't usually post on AIBU, I don't usually feel l have much to offer, but for some reason, OP, I've been thinking about you and your mother since I read your post yesterday.
My late mother went into a 'decline' after my father died - no alcohol abuse fortunately, but she became totally closed in on herself and her grief. I was close to my mam and very supportive and sympathetic, but one day I found myself saying to her 'Mam, you do realise that I've lost my father, don't you?'.
It's important to note that you lost your father suddenly five years ago, but your mother's grieving seems to have occupied so much of your space that maybe you haven't grieved for him properly. She's not doing it on purpose, no more than my mother did, but that's the outcome: you are all wrapped up in your mother's grieving - what's happened to your own?
From your mother's point of view - she may be aware that she's not doing what mothers are stereotypically ''supposed to do: support and comfort their children, but she just hasn't the emotional resources to do that now that the husband, who was her support, is gone. Maybe that's why she can sometimes function better outside the family at work or with friends - different dynamic, she's just her, not 'mum'.
That's total speculation on my part, obviously, but I think some of my mother's withdrawal was due to that.
The last thing I'd say is that 'reverse parenting' is very difficult because unlike actual parenting, you have no leverage over your parent. As you say, she is a grown woman and you can't make her do anything. I repeat: she is a grown woman and you can't make her do anything. So stop trying.
I found that I got through to my mother by forcing myself to see her as a human being, a woman, not 'mam', and by taking as much emotion out of the situation as I could before talking to her 'woman to woman'.
Maybe have a sit-down over a cuppa and say, as calmly and neutrally as you can manage -
'Look, mam, I know things are very hard for you because you miss dad so much, I miss him so much too, but it's very hard to be around you if you won't take better care of yourself. You're all I have now, and I love you and I'd hate if anything happened to you. It's your life, but I'd really really appreciate it if you could take better care of yourself, the drinking is really worrying me.
If it was Auntie... or your friend ..... who was like this, wouldn't you be worried about them and want to help them get better?
I'm not going to keep nagging you, but this has to be said: you need to talk to the doctor and get help. Please mum, I'm asking you to do this for me. But it's up to you. Right, end of. Another cuppa?'
Something like that worked with my mother, and she accepted some help around the house [=a miracle!] etc., and I felt much less worried about her being on her own.
Your situation has really 'got amongst me' and I wish you and your mother well.
I hope your mother responds and starts taking better care of herself; but you have to face the fact that she might not, and you have to plan how to keep yourself strong and functioning and alive and well and focused on your own family if that happens - an awful thought, but you know what they say on planes about putting your own oxygen mask on first...?
Take good care of yourself, stay strong, remember that worry and frustration don't help, and are bad for you physically and emotionally.
- one each for two grieving women.