Wow, Fiona, this is a tough one isn't it. Firstly, I just want to say Good on you for being 'ballsy' enough to want to help in what could be, a very messy situation. Sometimes I think, if I was doing a bad job with my dd, I would want someone to care enough to stand up and give me advice. Without it being preachy or rude kwim. But I don't think all people see it that way kwim?

You giving her mother advice could go so many different ways you know? Like, she might very well take it on board, she might be at the end of her tether and just think 'yep I'm going to give this a try' but then on the other hand, she might think that you don't know what your talking about because your DSD hasn't behaved like that around you? Quite often, I have found, people don't always appreciate the advice, especially when they still haven't taken responsiblity for the situation getting so out of control, partly because of their actions. However fiona, I guess, at the end of the day you just have to think, what's the worst than can happen? You obviously don't have a 'close' relationship with this woman, and your concerns, so it seems are purely for the sake of the child, or teenager sorry ( i know they hate to be called that lol) Your motivations are pure Fiona, and you ARE trying to help your DSD, so why not give it a go? I am sure you are able (from seeing your posts) to be diplomatic (for lack of a better word) enough, to be able to put it in words that aren't going to offend anyone. I think you need to stress to her mother that you have to work together, no matter what differences you have had in the past, to sort out the daughter. She's only young, and if she doesn't get help now, unfortuneatly it will only get worse, and she will ruin alot of chances in her life that come her way, and will end up regretting it later in life, and possibly even resenting people who didn't give her a wake up call. I know through the things I went through in life I would of loved people to stand up and help me, even though its completely different and I wasnt' doing the things she was doing, well I was but as a coping mechanism for the things that had happend to me. Hope you can sort things out for both you, your husband and your DSD's sake, because it really sounds like you love her as if she was one of your own, which is lovely to see. All to often you hear of the classic step parent/step child syndrome that is so totally strained and neither party could give two stuffs about the other kwim. Best of luck, let us know what you decide xoxo