Assuming you are alcoholic, it's up to you who and how you associate. My personal practice is that anyone non alcoholic around me is free to drink if they want. But I have no tolerance for drunkeness or alcoholic behaviour. It is so boring. I leave, and if it is my place, they leave, family or not. I have a firm boundary on this. I didn't get sober to suffer from someone elses drunkeness.

You make a good point about your sister not enjoying herself unless she has had a few. I found this when entertaining customers. If I wasn't drinking alcohol, they wouldn't either. And that resulted in them being unable to relax. They weren't enjoying themselves because they didn't have their usual social lubricant. I would almost have to insist they have a drink and relax. And when they did they were fine, and we had a constructive evening.

Over the years I have had very few problems with drunks. My mother and sister, both chronic alcoholics, I never see now. I tried hard but I learned that I didn't have the power to sober them up, so it's damage limitation. Neither were safe to be around my children, and both were unpleasant to me and my late wife, and my current partner. I don't need that.

It comes down to what you can handle confortably in your own sobriety. Your sis sounds like she drinks more than is good for her. By going out with her, would you be enabling alcoholic behaviour? Would that be the best thing to do for your sis? Or is she a moderate drinker, and the main reason for your discomfort is centred in your own problem with alcohol? These are questions only you can answer.