I think deep down in every alcoholic the want to quit is there. It's how loud the voice of salvation is screaming. I couldn't hear mine at first, it took the need to quit drinking to start this sober train moving.
Like you are doing for your loved one, my husband drew the line in the sand. He said no more, or the door. I choose no more! Once I got going the voice of "wanting" to get sober went from a whisper to a scream!
While you certainly can't make someone do this for themselves, you can draw the line as to what will be ok and not ok going forward. My husband never waivered I knew/know if I drink I will do it ALONE. Alcoholics need accountability!!!!