Your friend is right, unless she wants to get clean nothing you do or don't do will make any difference. Most of us here who have addicted loved ones have tried everything and nothing works, if love could save our loved ones, not one of us would be here.
You might try Al-anon or Nar-anon, to help you regain your balance and deal with this in a healthy way. You are in an even trickier situation than most of us, you could lose your job over this, or worse, face charges yourself.
I'm sorry you are going through this and hope you'll stick around for some support here.
Hugs