My nice is 18. She has a 18 month old baby. She has been staying gone for days at a time doing drugs. Her mom has come to me for help, but I don't know what to tell her.
I have some good ideas but where do we start with helping my nice see that she has a problem? And what's the first step to recovery?

I don't think you can force some one to see that they have a problem. One has to come by that knowledge by ones self. But follow through with the ideas you have and see what happens.
My concern is for the child. Who takes care of the child when she is gone for days? Does she receive public assistance?
If mothers behavior puts the child at risk, she must be reported and steps taken to make this child safe.