It is about quality of life. I used to take beer for my dad every Friday afternoon when I'd finish work early and we'd sit on the deck at the nursing home, drink beer and talk about the old days. Priceless!
You should check with her doctor and see if she is taking any medication that would be negatively affected by drinking a beer or two on occasion. If she is, and if she can't be trusted to remeber that she should not consume alcohol, you should notify the nurse of her area of this so that the staff can watch her at the happy hours and offer her ginger ale or some other soft drink instead of beer.