I think you should stay out of it. Many times here, the stepmoms try to intercede and help work out a situation gone bad and they end up taking the blame. Don’t do it. With the little info you gave us about the actual incident, it’s hard to say who’s at fault but from how you described both your Ex and his daughter are both being immature and need to learn how to handle disagreements like adults. It’s best if you stay out of it but if you’re compelled to get involved I suggest you simple email your ex and tell your daughter that you will be willing to help them reconcile when they’re ready and if they need you. Then leave it alone. 

I agree with Maxwell09. I am just a stepmom with no bio kids. I am curious as to exactly what happened to make a father just do that to his daughter. I normal parent that loves their children just wouldn't ice them out like that. Please do not take this the wrong way when I was you ask but w has your daughter ever disrespected her stepmom ever? Your ex is definitely wrong in this situation no doubt he should be their for this daughter. But I would just stay out of it because I think you trying to intervene will make things worst.

I think that both you and your ex made a big mistake here. You allowed a teenager control. If you guys were still married and your DD had a fight with her dad, she would still have to come to the dinner table every night and they would have to get over it. 

You allowed her to stay away from him which made the situation worse. Your ExH did not demand she come over or try and seek counseling or anything else to make their relationship solid again. You have both failed your daughter. 

If I was you I would call a therapist or 3, do some interviews and find one that will work on this complex relationship with the both of them. Other than facilitating the first visist, stay out of it and let them figure it out with a professional. 

She's afraid of being rejected or she's afraid of having to live by dad's rules? There doesn't seem to be many effective rules at your house if she's still on drugs and failing out of school. Kids will naturally refuse to spend time where they have limits and expectations in favor of the parent who let's them run feral.

Concentrate on fixing your daughter before you worry about fixing her relationships. It sounds like you are blaming her downward spiral on this single incident with her father. It is more likely that her problems started before that, which is why things came to a head at dad's. Does she have rules and consequences for breaking them?

You mentioned a therapist? How long has she seen this person? It may be time to switch therapists if her current professional isn't producing results.  

I wonder if the OP is blaming her ex rather than holding her daughter accountable and if that’s the case, has her ex husband ‘given up’ after realising BM is not encouraging a relationship with their daughter.

My SD behaved in a similar manner when she was ‘caught’, her reaction was to go running to Mummy who immediately withdrew contact and sent several solicitors letter containing veiled accusations of me bullying and frightening her children. This has lead to ongoing issues with SD behaving in an entitled way knowing we do not have the credibility to rebuke her (i.e. - she have options as to her living arrangements - running back to Mummy’s house, telling lies etc. Now she thinks she can treat one or any of us adults like crap and fall back on her ‘other’ family to save her.

There are often two sides to every story and from a SM’s POV, there's often a very different interpretation of events from that of a BMs. Eg. why on earth should a SM have a thief in her home. OP's Ex-husband and SM are a married couple and that means their relationship is the priority, it’s absolutely right that a man has his wife’s back and enforces standards of behaviour in his own home.

Perhaps its time for a little introspection, forgivness and reconcilliation. 

I'm sure I'm biased because I've been through this but I cannot comprehend as a biomom why you wouldn't do more than "encourage" a relationship with the other parent. If you were still with your ex your SD would have to deal with her father but you've allowed her to run away and avoid her issues rather than dealing with them.

My SD has run back to BM several times because we "mistreat" her asking her to do horrible things like clean up and brush her hair. SD embellishes stories and BM rescues her from our abusive ways. When this happens her dad leaves it up to her to reach back out. He's not icing her out but it's expecting her to own up to her actions and refuses to be walked over and disrespected by SD and BM.

I don't think SM going to your ex to have issues solved is being sneaky at all. A lot of step parents here have the bioparent parent their own kids. I also can't imagine a grown woman throwing a fit and going as far as going to the police over a lie. I think your daughter is probably guilty and is scared to go back and face her father. She may truly be concerned about being rejected because she knows she's wrong. I know from talking to my SD that the longer no contact goes on the more anxiety gets built up about contacting the person again. 

I've thought about this a lot and for me if my biodaughter ever was in this scenario I would setup a meeting with ex and the kid and talk through it together.