I'm not sure if the OP is serious or if he's still around, but I might have something to add here. I basically had her lifestyle for a long time, coupled with heavy depression. It's pure escapism. Weed addiction isn't something that easily discussed on Gaf because people can be quick to ridicule, but I'll just say that I've learned first-hand that regular weed-consumption isn't nearly as innocent as some people like to claim. Weed makes you feel okay about not doing anything with your life, and the longer she keeps living her life like this, the harder it'll be to quit. I managed to kick the habit, but it was a long, hard road.
My first step was joining this forum:
http://drugrehabber.com/. It's full of people going to similar issues, and it was vital in my recovery. Even if you can't convince her to join it might be useful for you to look around there - there are also plenty of discussion from people who aren't addicted themselves but just don't know what to do about their loved ones. It's full of smart people who are actually helpful and experienced with this kind of stuff. It won't solve all your problems, but it can be an important first step.
I won't be posting about my addiction in here again, but feel free to PM me. I was addicted for 6 years or so. Believe, the longer you wait with getting help, the harder it'll be.
And before people start attacking me (it's happened to me in the past): I'm not saying that all weed-users are addicts, and I don't think there's anything wrong with smoking something from time to time - but there comes a point where you have to be honest with yourself about why you're actually doing it, and if the time/money involved is actually worth it.