First, big kudos to your girlfriend for recognizing she has an issue and taking steps to address it.
What can you do? No alcohol in the house. And don't drink in her company. Why take the one thing she is battling and put it in her face? When my ABF went into treatment I stopped drinking. I am not an A, and don't have an issue with alcohol, so it wasn't a big deal for me to stop. I'm expecting him to refrain from alcohol, so I felt it was fair to partner with him in this journey. Not everyone has to do that, but it worked best for me. I learned when he was in treatment that even if I had a drink away from home, it created a trigger for him. Not worth it.
Find an AlAnon meeting, and start attending. She's going to AA, your side of recovery would be AlAnon. You'll learn a lot in those meetings, and will get support for yourself. Also attend an open AA meeting if you can. It will give you perspective from the A's side of things. You may end up re-thinnking your own history with alcohol.