Look, I'm not involved in this, and I certainly don't know all of the details that I'd need to make a good judgment. But I've known these people. Quite a few of them, actually.
Let me tell you right now that there's no way these people will ever be drug-free. They go in and out of rehab like pendulums.
Here in the Netherlands, we recognize a certain group of people as "long-term addicts" which require a great deal of attention. There's even a special group of heroin patients that are given free heroin because other forms of treatment are ineffectual or undesirable (after being addicted to the stuff for more than 30-40 years, detoxification can be deadly). These people generally have huge debts and are completely hopeless.
You're best off leaving her alone. It's her family that should help her, not you. To get someone out of this most likely requires a great deal of intervention, which is virtually impossible if she's an adult. If she wants to really kick the habit, she's best off moving to a different country where she doesn't speak the language.
Definitely what Dada said here. This is very true, as have the comments about "She's not your responsibility," and so forth.
However, I have known a few of these people who have been like this and DID *eventually* change. Eventually. On their own. Some influence was held by friends, sure, but ultimately, it was that they chose to deal with it finally.
I'll give you two examples. Let's call the first girl Emily. She was taking Martial Arts with me -- she was actually a higher rank. She more or less is how your friend was -- she got into EVERYTHING. She liked EVERYTHING. She was smoking weed out in the back of the martial arts studio once and my instructor was asking me where she went. I didn't know she was doing that at the time (who would be that stupid?). He caught her and put her on probation, hoping that he could influence her by saying if she did that again, she'd be kicked out/not be able to test (she was one away from black belt)/etc. Well, she said she learned her lesson -- but next week, she was at a Mexican restaurant on the corner of the strip the studio was on and more or less making out with a guy there (probably on Ecstasy) and then smoking -- she was 15 and this is the US -- so that's illegal. She got kicked out then. She continued this behavior and about 2 years later, I saw her -- she was pregnant. I had warned her so many times not to get wasted and screw her life up (we talked and hung out sometimes) and she always went back to habits -- I offered to help her get away from the stuff and help her go cold turkey (the biggest issue was weed -- there'd be some withdrawal, but it's not like she was doing heroin regularly or often). She said, "Yeah, don't tell me, I know I already ruined my life and I'm sorry I let you down." I was kind of struck off my feet and the only response I could give was, "You didn't ruin your life and you have nothing to be sorry for. Just please tell me you've stopped doing all of that crap now that you've got a baby coming." She had. I'm likely to believe her -- either that or the kid is impossible to kill -- the amount of drugs, etc she did would have definitely made the kid screwed up. Last I heard though, she was off of drugs -- but she did smoke cigarettes. Her family was full of smokers, so it's not TOO bad, and she's over-protective of her baby so she'd never do it with the little tyke around -- she'd go outside and make sure she switched clothes and cleaned herself to not smell like smoke at all... She eventually dealt with it, hopefully. Crossing my fingers that she's ok now.
The other, we'll call Jess. Actually, the girl I was dating for 3 years, engaged to, etc. A new guy comes along and offers a lot of new things and the like and she runs off with him and they get into that. Well, he's gotten her into drugs, etc. She already had a completely unrealistic viewpoint of the world and expectations that were just impossible (sorry in advance to anyone Vietnamese here -- but Viet chicks are APE-SHIT CRAZY -- but also very hot *sigh*). She's moving out soon -- but she doesn't have a job -- she's never had a job -- but her boyfriend she's with now, Mr. Weed and Coke, is going to be a LAWYER! He has a legitimate interest in those things -- so that's cool and I hope he does well -- but if they ever gave him a drug test, he's going to be screening through the charts... I don't know if he'll be able to make it through actual Law school. And certainly, his grades will make things hard. In any case, she's starting to do all these things with him -- and more or less, she's going to move in with him and the habits will continue. She tells her parents she has a job and that's why she's gone all day -- but they stay out of things and let her do what she wants. They think she has a job and don't touch her finances. She failed out of school in some areas and now she's "switching" because they didn't conform to HER. (she'd skip class and wonder why the professor thought she was a slacker)
With Jess, let me tell you, it is the SINGLE hardest thing I've ever had to do in my life and it still breaks me a lot. You have someone you're close to (I'd probably be able to say that she and I were a lot closer than you and this girl), and they're just basically DESTROYING their lives. And you fight and you fight and you fight and you want them to see it and be better -- but some people are just either 1) too stubborn or 2) too stupid. Unfortunately, she's always been that first one. But now she's running very close to the second.
That's why I've actually been more active at GW -- I've been trying to give myself other things to do and getting away from some of the negative influences. The only reason I started to drink heavily lately (I don't really drink at all -- and I don't ever get wasted, but I do still feel like I put my sorrows into the booze to lighten up and not worry so much about things) is because of the entire situation. It's just so obvious when someone is destroying their life right in front of your eyes, making all of the wrong decisions, and eventually... well, doing things that will go against EVERY MORAL FIBER OF THEIR SELVES. The girl who didn't want to be dependent on anyone or anything -- addicted to a few things now and probably moving in with Mr. Weed, Coke, and Law. Yeah... Great, huh? It eats me up, but I'm telling myself there's nothing I can do anymore. She needs to fall on her ass and realize things for herself. If she comes back to me, I'll be ecstatic -- but ideally, hopefully, truly, she'll at least find SOMEONE to get her off of that high or REALIZE it herself and not be bound to that shitty life.
As a final example, I'll give my little sister. She's done everything. (her personality is actually similar to my ex -- the only thing is that my sister realized it was time to grow up and that there are consequences) So Miss. I wanna be a model -- who now has a tattoo, piercings just about everywhere (and she's still fairly pretty), decided to get her life in gear. She's been sober for about a year, cut out all of the jackass losers that hooked her up with things -- and she's actually still able to be a model. She actually was doing a wedding dress photo-shoot last week. They let her hair down and it covered up the excess holes in her ears and the wedding dress can easily cover the tattoo. All other piercings are hidden by clothes or make up. And she's loving it and she has something positive in her life. But ultimately, as I'm making this very clear again, she CHOSE to do it HERSELF.
And unfortunately, that's all we can ever do. As much as it kills us and makes us want to rip our hearts out and the like, there is NOTHING we can do that will change THEIR mind. It's a mental addiction no matter what -- even playing a game can be a mental addiction that is unhealthy (*coughpeopleinkoreadyingfromplayingnonstopstarcraftcough* *coughkidsfailingalltheirclassesbecauseworldofwarcraftwashavingaraidcough* *coughbestfriendsgettingfiredfromjobsbecausetheyneedtoleadtheirguildinguildwarsorworldofwarcraftcough*). The only way to beat it is to realize it *yourself* and fix it *yourself.*
Try to avoid these people if you can, because it's only going to hurt you in the long run. Actually, the reason my little sister even got dragged into that was because she had that same attitude as you and I and everyone else -- "I want to help them." But we can tell how that went...
So yeah. That's just my five cents... and thirty dollars attached.
--Terin