I meant the thing about not sharing the past as more of a comforting thing, really.
We know they are drug addicts, we know they have, very likely, done things of which we would not approve, but not all of these things may, necessarily be "scary" things, maybe just things of which we don't approve.
I kind of look at it like this. A husband has an affair and the wife finds out about it. It is enough pain to know about the affair, she doesn't need all the minute details of the affair piled on to increase the hurt.
It's kind of the same with our addicts. We know they have used, stolen, been homeless. We don't need all the little details of what they have done to survive. It doesn't change or help the situation any.
Those details and the shame of those details are things to share in AA/NA with people who won't be hurt or horrified by it. It's not for your mom to hear so she can continue to blame herself or wonder where she went wrong.
Not that I think mothers are to blame or went wrong anywhere, but I think that it is a natural, although misguided, response when our kids screw up.