I feel your pain, feisty.
My sister is an addict, and thankfully she's on the path to recovery. Thinks looked bleak for a while, though, and I have been looking after her six year old son for the last year. At her worst there was nothing we could have done to get through to her. The only thing I could do was make sure Connor was safe.
I don't share HT's bleakness, but I do share the overall sentiment. Do what you can to minimize the collateral damage, but don't do anything under the guise that you are "helping" the addict. The only one who can do that is themselves.