Scarlett, welcome to the forum. My heart goes out to you, but the truth is there is nothing you can do for your sister. She is not willing to stop drinking, so she is digging herself an early grave. Her youth is the only reason she is still alive, but the alcohol seems to be catching up with her. You have nothing to feel guilty about. You cannot help someone who does not want help. Do what you are comfortable doing and are able to do, but also try to detach a little. If you haven't already done so, you might want to read some of the other posts here dealing with alcoholism and liver disease. You have a lot of company here. Feel free to vent at any time.
Scarlett, thank goodness you did get care of her daughter. That was a smart move. Now the daughter has a chance at a normal life. That is a gift you gave your sister, whether she realizes it or not. I went through what you are going through with my own mother, so I understand. I was traveling down the same road, and when I realized I was becoming just like my mother, it scared me enough to seek help through AA. I've been sober now for 23 1/2 years, but I was the one who sought the help and was willing to do whatever was necessary to get and stay sober.