The thing about love is that it doesn't matter when it comes to addiction. I used to think the exact same thing you do-- if she loved me and our daughter enough she would stop.
I've come to believe over the course of 11 or so years that she loves me and our daughter with every fiber of her being-- it's just that she's an alcoholic/addict.
She is still fully responsible for her behavior and decisions, and once I stopped protecting her from the consequences of such she eventually found sobriety. There are no guarantees-- she could relapse tomorrow-- but she's been sober for over a year and things are getting better.
Alanon helped me a great deal in this. Please consider trying a few meetings.
Take care, take what you want, and leave the rest.
Cyranoak