How to deal with an alcoholic sister?

My younger is thirty and has battled with alcohol since her late teens. Until about 6 months ago she had been living in the states with her husband (who is American) and their three children (the eldest from a previous relationship here). They had a volatile relationship to begin with and alcohol just seemed to fuel it further. As a result of her drinking in the 6 years she was over there she ended up in rehab twice and and on two occasions had the children temporarily removed from her custody. Both parties were partly to blame in what happened. Her husband told her enough and sent her to live in his mother in laws basement. Feeling at an all time low she inevitably turned to alcohol and a huge bender and mother in law who needed any excuse to send her packing saw her back here without her kids, no money and barely and posessions.

Our family has always been close knit and has always supported her with her struggles with addiction and depression so immediately took her in. We all felt horrible for her and she looked an absolute mess. In the past I have supported her struggles to the point where I myself ended up in counselling with the hell she put me through. So this time around I was supportive but still cautious.

Initially she worked hard to reestablish herself and do what she could to get her kids back, or at least establish some visitation, as her hubby was being extremely vindictive and would one minute work with her only to turn around the next and say he never wanted her near the kids ever. And at first she took all these blows but eventually it got too much and she started retreating to old habits. She would disappear for days only to return looking like a zombie. She started seeing an absolute dropkick and would blow off work and college for him. All her money started going to cigerettes and alchol and not the kids. Everytime I went to go see my parents they were a mess over how my sister was. And my sister was always going mental over how they treated her like a child (even though thats exactly how she acted!!). They paid for everything for her and only expected her to pay her back when she was able to.

My issue is this. Since all this has been happening me and my three and one year old have taken a back seat. My husband works away and we live fairly remote so I dont have any support other than him when he is home and my family. I would be lucky to see my family one day a month and its only if I drive the hour and half to see them. They are always too busy or stressed to come see me. Now they are brining my eldest neice back from the states. I am so confused with how to feel about this because I don't think my sister is capable of taking care of herself let alone a child and secondly i only feel that this would be rewarding her behaviour and not an incentive to get her act together. I also still love her though and think that maybe this will be what she needs to get better. I am just so sick of giving her another chance. I put my foot down and said that I would be no part of her life and she was not to see me or my kids until she got sober. But now everyone expects me to show up all smiles when my neice gets home in a couple of days!

I dont know what to do!! Sorry for the long story but would appreciate thoughts from people who have been here before. Thanks