Here is the thing. You screwed up with the affair. You have owned it, and are working towards regaining her trust. In no way am I minimizing that, but definitely I am saying you did not make her drink.
The thing about an addictive personality is that any little trigger will set it off. I learned that the hard way with my X. In life, there will always be issues. Sadness, happiness, death, physical and mental problems, you name it. It's her choice if she is going to pick up again when these things happen. Many, many addicts do. The ones who do not fight that urge every day, for the rest of their lives. It's a huge commitment only one person can make, her.