Welcome Rattler,
I am glad you found SR, because I think its a great place . I wish I had had access to it back when my mom was in her dark drinking days. She has passed, at 62- much too young.
Perhaps voicing your concerns to her will help, her and you. She might be moved to get help.
If she doesn't , there isn't much you can do, except for your own peace of mind. Al-anon can give you some support, and your sister as well.
this link may give you something useful. It helps a lot to know what is helpful and what is enabling. I hope you stick around, and the friends and family of Alcoholics is a good place for you to post as well. lots of folks who understand, and have experience to share.
http://www.soberrecovery.com/forums/...ook-study.html