Sorry for your pain, you can't help someone who doesn't want to be helped. May I suggest Al-Anon or Nar-Anon if there is a fellowship in your area. A drug is a drug, substitution doesn't work. It sounds like she was using you to stay clean and going to him when she wanted drugs.
She is not her disease, but responsible for her choices and actions. You can't make someone stop and you can't keep them clean and sober. You can't make them pick up, you don't have the power. Even in today, with 22 years of sobriety, no one can stop me from using, except my God. It is my connection to Him, that allows me that pause, to make the decision to stay clean, just for today.
My son was 25 when I came into recovery, he has been in 5 treatment centers, and in today, he is still using. He doesn't like what he would have to do to stay sober, he says he will never go to a meeting, he wants change but not willing to give up his pot, even though he knows, it takes him to other things.
All you can do is pray, detach, and focus on you as to what you need for your peace and serenity. She can't do for you any more than you can do for her.
