I'd wait for her to talk about whether she's still sober. If she mentions that she drank, just be understanding and say well you can always try again, or something. Alcoholics, especially new to sobriety, need understanding an support, and good listeners. I'd leave it to her to set the tone of the conversation. If she's still sober, give her congrats, and if not, give her understanding. Hope she's doin well!