No alcoholic will moderate or quit out of love for someone else, is my understanding. And thank goodness, b/c it would be easy to choose to relapse--'oh, so-and-so really isn't worth all the trouble. So now I can drink!'
It has to come from love of self, the desire for a better life, the desire not to die. AND the conscious recognition that drinking is a real problem. That's not in your hands.
I looked at my situation like this: the A in my life was married to alcohol. He had a family with alcohol, a life, friends.
I was his mistress. I kept waiting for him to leave his 'wife'--and to him, promising that he'd divorce the booze, soon, someday, when the time was right, was just (empty) words that let him keep all of it. My mistake was putting my life on hold, waiting to start it until he got better. He used me, and I let him.
I suggest Al-Anon as a great way to learn about alcoholism and addiction, and the limits of your own power to help someone you love. Good luck!