Its going to be difficult but you have to try and make her see eye to eye with you. I dont think lying to her is going to make anything any better in the end.

My bf smoked a few times and decided not to smoke anymore. He never did get high. I smoke everyday and he knows it. He teases me about it if im spazzing. He even buys me some weed from time to time. Its cuz I am honest. You can be honest too!!!!!!