Have you told your wife this?
It may be that alcohol has affected her adversely, too. As you know, you don't have any control over her, but you can choose not to be around her. When she goes into her negative cycle or complaining excessively, can you tell her she's not much fun to be around when she's like that, and then leave and go do something else?
All we can do is be a positive influence on others. I feel for you, I've been her and I've been in a relationship where I was you.