Wow, Kat. The addictions forum will for sure help more than I can, but I can see your dilemma. I'm not sure allowing a toxic person like that back into your life is such a good thing. Sounds like you feel as if you owe her something since she raised you, but you are both grown up now, and I feel relating on an adult level means allowing her to take responsibility for herself. If she is unwilling to get treatment for her addictions and self-destructive behavior, I can only see more turmoil ahead for your family.

On the other hand, maybe she is reaching out for support to help her help herself.

In either case, I would be sure to set firm boundaries on the relationship until you find out what she wants from you. I think you did the right thing to remain somewhat aloof.