Comparing ourselves to others doesn't really help-it leads to resentments-anger,bitterness, jealousy,envy, hatred and resentments are the quickest thing that leads us back to the bottle.
The only thing we can do is do what we need to do ourselves to get sober. It doesn't really matter what your sister does and people can't be helped unless they want help. In any event, we can't help others until we are ourselves fit and healthy.
I would concentrate my energies on getting myself sober and building my own sober life.