Ditto to what everyone else said here. If you can quit, and either do it with her, or at least do it publicly, it'll do wonders for your 'creds.
McWeedy was always harping on me about the fact that I was a "drunk" in college, and I should know what it was like to be a teenager who liked to indulge. And who was I to judge him for doing the same thing?
Ouch.
If I was still drinking, I could try to quit with him. I don't know if it would work, but it would at least set both the example AND the expectation. The example is that quitting IS possible (if I had a nickel for every time I heard how hard it is to quit...). The expectation goes along with what the other said: it's not tolerated in your house, not by her, and not even for yourselves. Might be a small Pyhrric victory, but it does take away one of the most potent weapons difficult child's have against their parents ("you just don't understand, so don't lecture me!").
Even though McW is 18, we follow the "not allowed" rule in our house - that includes cigs. We can't control what he does outside our house, but we can control what happens IN our house. wife raids his coat, bookbag, room, and everything else frequently. She's probably thrown away 100 dollars of cigs, lighters, and other stuff in the last two months. Doesn't stop him from doing things, but he doesn't do them around us or in our home.
It may not be appropriate for your child at her age, but we also assert the right to control the "benefits" he receives, based on behavior. When he stops answering his phone, we take it away or turn it off for a week. When he disappears overnight without permission, he loses his car for a week (work and school only). He's already lost the right to have friends over, and we have periodically told him his girlfriend is persona-non-grata as well.
Finally, McW is on diversion, and I've let him know that if we find anything illegal, comes home drunk or stoned, I'll be the first person to call his Diversion officer. I didn't win any nominations for Dad of the Year, but he got the message.
Not in my house.
We can't control what he does outside our house, but we have every right to use everything at our disposal to reward/encourage positive behavior, discourage negative/harmful behavior. It doesn't work extremely well, but it does work for a while after a benefit is withdrawn.
Also, I'm in a little different boat than you - I'm trying to mitigate the harmful behavior of an "adult" teen still living in my home. I've accepted that I can't control his every move, and can't control what he believes or how he feels. So, my goal is to set limits within my own home, and within the limits of whatever benefits he receives from us. Maybe he'll learn, maybe not. But at least it gives wife and I some measure of control over our household, if not over McWeedy. At this point, while he's at home a little control is better than no control at all.
And most importantly, I'm correcting a mistake I made two years ago when I turned a blind eye to his pot smoking. That was the wrong message to send, and he's never forgiven me for changing my mind a few months later. Regardless, though, I now tell him that I will not tolerate acting out in my home, nor will I do anything to condone his acting out when he's away. No "boys will be boys" or "everybody does it" BS excuses. It's simply wrong, especially for him, and I'll never again give him any reason to think I believe otherwise.
Don't know if it will help, but I won't give him one ounce of support (real or perceived) for the bad choices in his life. McW is 18, so I'm probably wasting my time, but it's all I have left (other than booting him out). Maybe it would work better with a younger person.
Some wise CD'ers here, in the past, have reminded me that this is the simple "do to get" philosophy. When paired with the "don't do, don't get" corollary it might work very well for a younger difficult child. Jury is still out on how well it works when they get to McWeedy's age. Check back in six months :crazy1:
Prayers for both you AND your daughter.
Mikey
PS: I'd also like to suggest that you get professional medical help for your daughter, if possible. My doctor told me that nicotine is more addictive than cocaine - especially so for younger, developing brains.