Wow... are you sure you and I don't live in some kind of parallel universe to each other? We're even the same age... and I know exactly what you're talking about. Ive felt that same rage so many times... my sister did the same thing, and it only felt worse when I learned that my parents were not going to press charges. And so things continued... and I went from feeling rage to hurt to depressed and right back to rage again, for a variety of reasons, all tied to the same set of problems.
I've had to learn that, in order to stay sane, I have to continue to put myself first. I've got a career that's still in its infancy (I'll begin my third year of teaching in the fall), I've only been married for 2 years, and we just bought our first house back in September of last year. So, I absolutely cannot afford to allow my sister's path of destruction to pull me down, especially if I ever hope to have my own children and be the supportive, strong mother that my kids would need.
Here's how I've detached: I've gotten to the point where I purposely try to know as little about her progress as possible. If I hear from my sister, I am always happy to talk to her. But I make sure to avoid talking to her about her drug problem. If she brings it up, (which she actually will now, since she's in recovery, although she will relapse occasionally) I try to be as positive as possible and move on. I might say, "well, I sure am glad to see this change coming about." or something to that effect... but I refuse to ask about it.
I've also learned that I cannot talk to my mom about her. My mom is still in denial about my sister's prognosis, and just very well may always be.
I know it sounds so hard to just up and look the other way; but that's not really what this is. I am very aware of her condition. But by doing everything I can to avoid the hourly updates and to make sure the majority of my energy is devoted to keeping my life on track, I can at least protect myself from some of the unnecessary heartache and worry. After all, we've had enough of that already, right?
I'm praying for you girl! If I can get to the point where I am more of a bystander than a character in the plot line, I know you can too!