No one can tell you what is going to happen with your girlfriend.
The best advice is to focus on yourself so can be as mentally, emotionally, financially, etc. prepared as much as possible for whatever happens.
My personal experience is that when my xah (we were still married then) returned he was dry for 10 days and relapsed. During that 10 days the manipulation, blame-shifting, and guilt tripping were at an all time high - much higher then at any other time of our relationship. His emotions were all over the map.
He went into rehab again (different program - longer and more intense) a year after our divorce was final and then moved on to a sober living environment. He stays sober there and no longer blames, guilt trips, or manipulates me. We still have some contact because we have four kids. That has been about 10 months and so far if he leaves there, he drinks.