I'm Losing My Gf Of 3 Years To Drugs...help

Hello, I'm a 27 year old living in Canada. I've been dating a girl for 3 years now. When we met she was really into partiyng, but slowed down after a while. I am totally against drugs myself, and have never done them, and tolorated her occasional use. This went on for 2 years, but I grew unhappy enough and ended it after 2 years. We spent a few months apart, and she eventually got herself together, stopped using, changed her friends and lifestyle. As of late she's been hanging out with a new group of friends, who like to party. I'm talking about pot, ecstacy. She said she now wants to occasionaly start using again, and can control it, and that it would never affect us. I don't believe this to be the case and She did mushrooms on Fri. night and told me she just didn't care as much at that point. She said it's not that she's choosing the drugs over me, but rather the freedom of choice. I'm so torn up over this, and I really need some advice....please help.
You should most probably give her space. Let her see that her life in that light isnt positive in any way. She'll be back.
You should tell her that maybe she can handle it and maybe she cannot, but you have no more time in your life to waste finding out just to potentially have your heart broken again. Ask her why after past problems does she believe this time will be different. (Druggies are good at lying to themselves which is why they often seem so very sincere when making excuses.) If she can't handle her own life, how will you be fulfilled with her as your other half.