Well, the boundary is for you, not her, so you don't have to declare anything to her. You can make your own boundary that if you become too uncomfortable you will leave. I see no reason you should avoid your whole family unless you are too uncomfortable around the drinking/enabling/random dysfunction. Your boundary can be that you will take care of yourself and recognize that your parents and sibs will have to take care of themselves--you don't have to be ruled by a sense of familial obligation.
Congrats on your sobriety!