there isnt a whole lot to do to help seriously - just keep your distance for the reason you dont need to get in trouble, seriously. Your friend has to want to quit or find the reason to quit themselves with meth its just something they think they need. You keeping your distance is the best for both of you because if your friend gets mad at you they will just go do more and find some way to use you. The trouble part of it is the worst - just being associated with them makes the cops frown on you.
Distancing yourself also will at some point clue your friend into the possible path of cleaning themselves. When you lose enough friends you wonder why.
At least thats what happened for me.
I lost everything a few times but not anymore Im done with that life its so not worth your own life!!