I've worked extensively with people on crack and meth. I strongly suggest you keep going to Nar Anon and use the program to help yourself. It's likely things will get worse before they get better.

If your sister has aged 10 years in the last six months, it's not a good sign. She could very well be in deep trouble and fully involved in his lifestyle. It's important that you, as a loving sister, learn how to best be there for her without making yourself sick in the process, triggering your own mental health issues or enabling her. It's a very tricky situation.

I commend you for seeking the help of Nar Anon. Please get the recommended books, study the program, do The Steps. In my experience, it usually takes a minimum of three months of regular attendance before the basics of the program begin to seep in and really make sense on an emotional and intuitive level.

Nar Anon is there to help you so you don't go downhill in your efforts to cope with your sister's distressing choices. I know you love your sister and want to help her, but right now the most important person to help is yourself. Nar Anon can help you take care of both your physical and mental health so when your sister is ready, you will be in good shape to offer her healthy and loving support that lifts her up without dragging you down.

I wish you the best.