Hi Wandering,
I have had a bad experience with opening up to my family in the past, but I've always been labelled as "the little sh**," and so was not taken seriously.
It seems as though you really care about her, and that she has been a positive female role model in your life--other than the pill-popping.
Is there a time when you know she generally feels calm and relaxed?
Frame your concerns as a concern for her, not so much a plea for how you have been personally hurt or how others have been hurt. This may help her to be a little less defensive (though you should expect some defensiveness).
Also, pay her your sincere compliments (like what you've posted) before diving into your concerns. People take things much better after a compliment (especially a sincere, heartfelt one) than when confronted right away.
If she is a true addict, she will get defensive and get her dander up. You might want to try to practice for that possible scenario. How will you plan to remain calm should she become abrupt and abusive? Under what circumstances will you leave? How might she react? Can you come up with a calm, loving response to her possible responses?
She may really want help, but become resistant to it. Here's something just as an idea in my head, if you need some words to start with.
"Mom, I really appreciate all the sacrifice you made for Brother and me. I have always looked up to you so much. I love you, and so I hurt when you are hurting. It seems to me that you are hurting right now. Have you considered the possibility that the pills you are taking are affecting you in a bad way? What would you like to see happen? How would you like your life to be different?"
If she becomes combative, you could say something like, "Mom, I can't deal with you if you are not going to be calm. I'll talk to you about it later," and leave. Let her scream her epithets at you, if she wants. Don't let them get to you. If she screams at you or gets abusive, remind yourself that it is not the mother you know...it's her addiction.
I'm not a pychologist, but did graduate with a minor in psych. So give what I've said whatever value you want.
I would also strongly suggest you read the stickies and maybe some other similar issue posts, if you can find them, before confronting. Perhaps someone else out there can give you better advice and tips.
I was 33 when I "woke up" to the rubble of a life around me, too. God Bless you in this endeavor. And remember, there is only so much YOU can do. Her life and decisions, ultimately, are up to her.