We been together for a year and everything was going great. The last 3 months the lying started, and hiding lots of things from me. Now, I'm going to be away for a year, and I love her with all my heart, I would give her my life. I want her to be back to normal, like when we first met. What should I do?

Get the romance out of your head. If the lady needs help make sure she gets it, and don't be so in love you settle for BS, from a flawed human. You have been letting this go for 3 months without confronting it? Unbelievable!

I doubt that this just started, you just found out, or noticed. But now you know there is a problem deal with it directly, and don't let your heart make you sloppy, and not proceed with caution.

The heart you save may be your own. She might not deserve all that love.

Talk to her, if she is willing to stop, then work at it with her, if she is not, then is a drug using girl what you are looking for? If you are not, then leave before you become even more involved. She sounds old enough to knows what she is doing with her life, she is not your resposibility.

Yea if you're comfortable to confrot her then I think you should!
Think first though if you think she will get defensive or aggressive about it then think about how you can work into the conversation! Let her know you'll be there for her to help! Tell her know how much it's hurting you and how much it hurts to see her like this! She should be able to see how worryed you are, and that may be enough to kick in a drive to try and quit! Do some small research and find out the side effects consequences... Understand it so you can explain it if needs be... Sorry if this was a. It all over the show! Things like this worry me I know how bad it is to have someone close have a problem, my best friend suffered anorexia and she was terrified to tell me I still cry thinking about it I was so worryed about her!
Hope you sort everything out!