Hi ch1, speaking as a sober A, it is very hard to quit unless you're lucky enough to have one of those moments where it all becomes clear. Getting to that point can take many attempts and years of trying. You EXAGF isn't there yet.
What part do you play in this? You sound like a guy with clear boundaries in that you won't be around her when she's intoxicated. There's nothing much you can do because she's obviously chosen to drink, and far worse, chosen to drive. Not all drunk people get behind the wheel.
The 3rd DWI is fortunate if she's driving drunk. It might just save her's and others' lives. If she opts for rehab again, and calls you sober you'll have to think about whether you want to be dragged back in.