JustJo,
I feel for you.
I am an alcoholic and I went to detox about 7-8 times.
It took me a long time to finally get it.
I am reading "Beyond the influence" and it is the best book I have read so far about the disease of alcoholism.
I highly reccommend it. It does so very much to explain alcoholism from a medical and research standpoint. I really did not know why I drank either but this book explanes a great deal. Much of the book is here in a sticky.
I wish you and your sis the best,
Ted