I am very sorry for your loss.
I think the relationship between you and your sister and your mother have many different components. First, there is a rather large age difference between you and your sister. Second, you lived closer to your mother then your sister did.
I know siblings of various ages who grew up in homes with alcoholic parents and each one of them have very different views on their life growing up with their parents drinking. Some of them found al-anon or AcoA (adult children of alcoholics) groups and have worked through issues. Some hold onto resentment and anger allowing that to corrode away at their own happiness in life. Some have buried it deep inside and wish to never speak about it.
AS much as it may hurt, accepting that your sister has chosen a different path in life then you did, may help you find some peace with that.