I have a suggestion, maybe you can offer to take her to an AA meeting with you.
It sounds like the rooms helped her stay sober for many years so it may work again and there may be someone who is a really good Sponser that can take over for you and somehow reach her better as you are new at this.

Sometimes my husband would come up against a similar situation and the AA group would organize some type of intervention. You may want to go to a meeting as soon as possible and ask around. I get the feeling that this friend of yours is not really capable of helping herself, even if she had done it in her past or even helped others.
I would not let her go any longer taking all those drugs that can cause her to OD.