Grits, you need to keep a healthy distance. You cannot rescue her - she can only save herself. Think of your own recovery.
I recently went to the rescue of a (close) friend from my relapse prevention group who had embarked on a bender. I was so shocked and devastated by her deterioration that I inanely went and bought a bottle (then more and more). I was too vulnerable to deal with her crisis and too blind to realise that I was out of my depth.
In a nutshell, I allowed her problem to become my problem!!
You're a good friend and obviously care about her but you must look after yourself. Be there for her only when she's sober or you could end up being dragged right down.
That's not selfish, just sensible.