Nothing the mamas do or don't do, nothing the girlfriends door don't do will change an addict who doesn't want to change. And if the addict really wants to change, nothing any of us does will stop them.
It's as simple as that, a hard lesson for all of us to learn and accept, but the hard truth nevertheless.
Don't blame anyone except the person who makes a decision to pick up drugs. Therein lies the problem, therein lies the solution when the willingness arises.
Addiction hurts every one of us. Please let's not hurt each other with blame and shame. Especially those who have tried to offer heartfelt answers to your original post. Ouch.