My mother is an alcoholic, and no amount of love, support, money, reasoning, begging, or pleading could get her to stop drinking. Unless an alcoholic decides to stop drinking herself, there's nothing you can do to stop her.
In my Mom's case, she eventually hit bottom, found AA, and was clean and sober for about 10 years. Unfortuantely, a few years ago she started drinking again. She hid it for a while and then after we figured it out, she acted like she was a normal social drinker, even though it was obvious to the rest of us that whe wasn't. I'm just glad she didn't make a drunken scene at my wedding.
None of her children have cut off contact with her, but her drinking certainly strains her relationship with all of us, especially my youngest brother. He bore the brunt of her alcoholism, since he was raised by her, but my other brother and I were raised by our father.