I would not follow Punkey's advice, not because there's anything inherently wrong with it, but because the chances are very slim it will be effective.
We all seem to share a history of growing up in dysfunctional families with damaging parents.
In my case, as in yours, my mother was the worst offender, and in my case as in yours I strongly suspect that a mental illness was involved (although to what degree alcohol caused or exacerbated the mental illness I can't say).
Like you I would often say words to the effect of "I love my mother but..."
Without going into details, at the point when our relationship was in its greatest state of ruin and destruction I asked myself if in fact I actually did love my mother.
There was a time, before I was 10, when I had every reason to love her dearly and I did, but after 30 years of a twisted and hurtful relationship I felt it was appropriate to reassess my feelings, and you know what? I came to the conclusion that no, I did not love her. Whatever real love is, as opposed to psychological and biological bindings, it had been extinquished long before.
What was driving my continued engagement with her were those bindings, habit, unrealistic hope, and guilt. How could I not love my mother? What sort of person doesn't love their mother. It's OK to dislike you mother and even, at times, to hate her, but to not love her?
There was nothing I could receive from an ongoing relationship with my mother other than poison and pain, and, as importantly, there was nothing I could give but anger. Over 30 years I had exhausted patience, hope, sympathy and, I realized, love. Other personal relationships as well as my health had suffered as a result of this toxic exposure.
Although I was almost ready I just couldn't cut the bindings, couldn't let go of the feeling that there had to be more I could do to turn her life around and even if there wasn't, it was my duty as her son to not abandon her. All the poison was just the price I had to pay to be a good person.
I tried one more time to talk to her, but of course she was drunk. There was never a time when she wasn't, but I let it all out. Not with anger or disgust but with pleading desperation. I told her I knew she loved me and I knew she needed help but I had to see some sign that she understood what I was feeling; that she actually wanted my help and my love.
She rose up out of the tangled sheets of the bed in which she was laying and turned to me with drooping mouth and heavy lidded eyes and said
"You son of a ****! You think you're so wonderful!"
In restrospect I'm surprised I didn't punch her in the face (seeing that look of a drunken hag usually raised my anger close to that point), but instead I barked a chopped laugh. It was absurdly funny, the way insanity can be. I got up, left the room and saw her again only one time when my nephew got married. We didn't speak and I had long been cut from the will, but I couldn't care less.
Whether or not this describes an option for you, I've never looked back and so if it may be, I urge you to consider it.
The one downside is that I've learned it's possible to send an otherwise important person in your life into the void. At first it seems its impossible but once you are able to do it, it becomes too easy to do so....and, unfortunately with people who don't deserve it.
It's like a secret weapon and you have to be very careful how you use it.
But that's Life right? No easy answers.
My brother and sister chose the more conventional and less satisfying route of remaining enthralled by our sick bitch of a mother. We have great relationships today because they don't begrudge my choice...in fact I think they wish they had followed it.
Now that's she's passed on (and in a most horrfic manner that suited her life's narrative) we're all back to square one except that I have had 30+ years of peace.
Bottom line: You need to decide what is best for you relative to an ongoing relationship with your mother, but you should not feel that you haven't any choices. The best choice for you may be one which others cannot accept, but then they haven't lived your life.
Your mother was sent to you by your genes, and not as a test of your morality by God.