You are #1
Sorry to hear about your girl getting hurt but dont beat yourself up about not being there. Your priorities are in good order and you are WINNING the battle with the beast, follow your good instincts and stay strong.
Alcohol causes us to do stupid things but hitting a woman is not acceptable, I hope the police were called and the jerk gets prosecuted. I can only imagine what would have happened if you were there... you might still be in jail or the hospital.
I'm glad you got to spend some time with her and talk. Hopefully that will continue.
Take Care