Girlfriend hiding something.?

Well, maybe she sees things like I see things. I don't necessarily think she is lying to you but weed is not that serious. It's nothing really. It's natural, it grows in the ground and doesn't need to be made like coke or heroin. So, she knows you don't like it so decided to not tell you. There's really no big deal to it but you gotta do what you gotta do so if you can't accept it then you should move on but never try to change anyone to be what you want.