From what you're written about your sister, I think you two will be fine. On another note, my sister-in-law, after years and I do mean years of heavy drinking, quit cold turkey. She didn't got to AA or anything, she just quit. I was absolutely amazed, because she LOVED her wine and drank every night. She's been off alcohol a year now, and drinks her "mocktails." I asked her why she quit completely, and she said she tried to cut down, but couldn't. It was either all or nothing.