As I'm not sure exactly what the situation is that you are describing, I'll answer as best I can in a generalised way.

If she is not finding it unpleasant enough to be concerned yet, perhaps there's not yet much motivation for her to look at it in the same way you are seeing it... However, if she has begun to find it upsetting, or spoken to you with concern, but is staying for reasons like "maybe I won't find someone better", or "but I love him" or "he can change"... there are some points you can make that might help to get her thinking in a reasonable, healthy way.

- There is plenty of evidence that various kinds of abuse or mistreatment or behaviour in a relationship foreshadows extremely violent, even deadly, behaviour in the future. Ask her how long she planned to live, during her happiest moments in life, and make it real to her that a woman's choice of boyfriend or friends or partners can be quite literally life-endangering. Have her read some information about the factors that predict extreme spousal violence and even murder. Oprah Winfrey quite often does shows on these sorts of topics - if you can find one of these for her to watch, it could be very eye-opening. You can also find psychology research online or in self-help books that can be eye-opening on this subject.

I had good references for one of my Mahalo pages on this subject, but unfortunately I've just noticed that my Mahalo page is not appearing properly. My work is all there in the online forms, but it doesn't appear. I'm really disappointed about that and I'll speak to someone to try to get all the information to appear. Meanwhile, here are all the references for my page:

http://www.bu.edu/police/prevention/domestic_violence_myth.htm
http://family-marriage-counseling.com/resources.htm
http://www.relationship-institute.com/freearticles_detail.cfm?article_ID=148
http://www.scstatehouse.gov/citizensinterestpage/SentencingReformCommission/RetreatPresentations/4QuestionsAboutTreatment&CorrectionalPrograms.pdf
http://students.usask.ca/wellness/info/mentalhealth/relationships/healthy/
http://www.sciencedaily.com/releases/2008/02/080208172104.htm
http://www.dailymail.co.uk/sciencetech/article-1119424/The-mathematical-formula-proves-couples-NOT-sex-date.html
http://www.drphil.com/articles/article/501

-Also, ask her what she imagined her husband and father of her children being like, when she was a little girl. Ultimately, choosing and staying in problem relationships can be very largely a problem with a woman's self-esteem, and understanding of what to look for and require in a partner. There are many great books and resources that can help women who have had a situation that has lowered their self-esteem and expectations. I recommend the work of Laura Schlessinger and Barbara De Angelis for this.

She needs to understand that good quality men.... Prince Eric from The Little Mermaid... Aladdin... or heart-throb characters she loved as a teenager... actually do exist. (While of course they will not be perfect, and will not be princes or rich/famous rock stars, etc.) But these "nice men" who you imagined getting married to as a little girl, and who consider it important to be a responsible, high-quality person, and treat a woman as a delicate and valuable thing, exist. They are what women should be looking for if they don't want to be on Jerry Springer or Cheaters one day; and they are not out of reach for any woman who can offer good treatment to someone else, who respects herself, and views improper treatment as not acceptable. And it is possible for any woman who doesn't feel this way about herself to reach that point.

(Has she seen Jerry Springer or Cheaters on TV? Does she realise that making the wrong choices in relationships mean that she becomes one of these sad people that everyone else is embarrassed for, and feels sorry for? Would these shows give her the motivation to make choices that will prevent her from appearing stupid to other people, for not being able to see what their situation really is and what choices they should and shouldn't be making?... Shows like these have definitely motivated me, when I was younger and less experienced, to keep making the right choices, see the consequences of things in advance, and do what will help me to respect myself.)

For help with self-esteem and self-respect, I particularly recommend the work of David Burns, as well as Barbara de Angelis and Laura Schlessinger mentioned above.

Here are the links to the articles I have written recently on these kinds of topics:

http://www.mahalo.com/how-to-avoid-a-broken-heart
http://www.bukisa.com/articles/231467_is-your-love-interest-genuine

Best of luck.

No matter how difficult it is to accept, I'd say that if you push her or nudge her, she *may* follow the worse course all the more. That is how it normally is with the teens.

Before anything, how good on terms are you two with each other? Does she gel with you well? If so, take her along for a shopping spree one day, followed by a nice dinner and desserts. Sort of a date between you two. Talk about things she's interested or enthusiastic about. Does she love dancing? What form? Talk about it to her. Is she in to sports? Which sport? Speak about it with her. In short, try to create a nice atmosphere between the two of you and then take it easy toward the topic of interest. However, do it in a way she doesn't really realize that you'd been wanting to. At the same time, don't be too effort full when trying to do it. Relax and enjoy the time with your step daughter above all. It is common psyche, a human listens to only the person who he feels good about, likes, respects amongst other things. Become that person for her and take it from there.

Alternatively, try involving her friends in to making her understand. Friends are of our age and we tend to understand and stick by what they approve of, many a times. Try making her friends see the point, and they might "persuade" her successfully in their own way. However, understand that all of this *may* cause to an issues between you and your step daughter, especially if she doesn't approve of you talking about her relationships with her or anyone. It might backfire if proper discretion is not undertaken.

You can also get the father involved at some level unless it is not a push for her, to ease it out for you.

Best,
Browneyed.