Well only you know your daughter and only she can do this anyways.

Thirty pounds in one year is actually really good. And if nothing else has changed chances are she is doing good. Though keep your eyes and ears open is never a bad thing. Your a worried mother and for good reason...thats your baby!

Maybe sit down with her sometime and calmy a just tell her "look I am a worried mother and I am trying not to jump to conculsion but I am just so scared to see you go back down that path". Honesty is the best policy and being honest isn't going to make her use more.

I really hope your fears are unfounded and that she is clean. Best of luck to you and Happy Thanksgiving!