how you can subject your daughter to this kind of behavior. Her life must be miserable. It is your responsibility to keep her safe and in a peaceful home. Your SO may be a good father to your son, but he is not a good parent to his daughter.

Please keep in mind that if someone in authority ever does believe your SD may have been abused, they will remove all children from the home, not just SD, during the investigation. Do you want to run that risk?

It sounds like this girl has serious issues.  Has she been for counseling?  How much of the problem is her father?  Does he appropriately discipline her?  Are there serious consequences for her seriously bad behavior?  It sounds to me like he's failing as a parent.  Either there is something wrong with her that needs to be addressed, or his parenting is abysmal, but either way, he is not doing what needs to be done.

I could not live like this. After the police had been called more than once, that would have been my limit.  I also could not tolerate my 7 year old being mistreated by a girl 5 years older than she is to the point that people from school are contacting you about it.  That is NOT fair to your daughter, and it is your job to protect her. 

What is your financial situation?  Can you leave, or afford a place so that you, your son and your daughter can be away when the SD is there?  Even if you are willing to tolerate another 6 years of this (assuming that this kid ever launches), I don't know how you can in good conscience keep your daughter in the situation you describe.

«My bf could do a better job at parenting her, but he's scared it'll push her even farther from him.» That tells it all and that is the problem IMO.

I don't see how things can get better if the girl's father is not willing to parent her.

Stop biting your tongue when she is around and being mean to your daughter and your man. Go off on her and make her not want to come back to your house. She is literally terrorizing your daughter and you feel like a prisoner in your home 50% of the time and you’re worrried about what??? Your pansy man’s relationship with this budding sociopath? What else is more important than your and your children’s well-being? If your “man” can’t control his child you either need to kick him out (most desirable option but you probably won’t do that), remove yourself and your two children, push her out by being scarier than her or make daddykins see her elsewhere.

This is no way to live!  

I get infuriated reading stuff like this. This man does not deserve to have a relationship with you if he puts you and your child in harm’s way!  His daughter is a loose cannon and you should demand that your home be a peaceful sanctuary not a prison. Geez! 

First, realize you can never change bm or what she is saying. Your sd is a victim of PAS. I have 2 sd's who went through the same thing, one is normal, one is a nightmare. bm has no rules  no boundaries at her house which resulted in my sd sleeping with an 18 year old at the age of 14 out at her house. funny thing is that we have majority custody and it doesn't matter, it still happens. from the age of 12 on up, you may have a nightmare time with your sd or she may straighten out once she is an adult. Surviving until then, that's the big issue. Your dh needs to set some rules with consequences. He's in the fear mode of losing her phase. that will just make it worse. he needs to step up and parent. and ask questions when your sd comes at you all with craziness. such as when she said, " you aren't even my dad". have him hit it head on and counter with " where is the proof of that i would like to see it". or "how did you come to that conclusion". basically you will have to retrain the way she thinks and speaks and develop critical thinking skills. if she's just spewing stuff her mom has said, then you need to question those things she says. questions like "ok what makes you say that" or "how reasonable does that sound to you". iinstead of anyone just getting mad and dismissing it, question it. if she's like "mom said that" then say "but we aren't talking about your mom we are talking about you". she's getting old enough to be able to shoulder some responsibility for what comes out of her mouth. I would also work on basically deleting bm out of your house as much as possible since she is so negative. only have your dh respond to her via email(u can keep in case of court) and keep them logical. courts do not like emotion, they like fact. he doesn't have to respond to hateful texts. this is a long hard journey and in the end it may fail, but in the end you all can say you did the best you could.

The seemingly never ending parade of SParents who are with the most wonderful partner in the world ... .but... that partner is a useless waste of parental skin is increasingly mind boggling to me.  For the decades I have been a SParent nothing has changed in this regard other than possibly it being even more prevalent.

My suggestion is that  you take this completely out of the hands of the BioParents and get this toxic crotch dropping hauled off in handcuffs for violence, theft, etc, etc, etc.....  It is too  late for parenting to fix this... It is time to let this crotch dropping live the life of abject misery that she has earned.

12yo is plenty old enough to know right from wrong regardless of how crapily she has been parented and it is plenty old enough to feel the consequences of her choices.

Keep it out of the family law court and get it into the juvenile criminal courts where rather than cater to this bulls shit they confront it.  Get her arrested and get an RO keeping her the hell away from your home and  your kid(s).  How that will play with Mr. Wonderful.... doesn't really matter IMHO.  That is not important in this context.  Protecting yourself, your home, and  your child from this toxic spawn is what is important.  If your DH so much as whines about it.... he is not the wonderful soul mate you think he is.  He cannot be a wonderful parent to anyone while growing this toxic kid.

Bring the full force of the available consequences down on her like a ton of crap in a one pound bag.

Confront the behaviors, zero tolerance, call the authorities when she violates the law... lather, rinse, repeat.  Sadly it is not this kid that is the problem. It is your SO and his X that are the problem.  The kid is just the symptom of their failure as parents and people.

She likes calling the police.... so see how she likes it when they are called on her for her thieving, violent bullshit behavior.

All IMHO of course.

Protect your children, draw the line in the sand and stand by it. I had to do it with my DH when his daughter was bringing random men home for sex and one had a criminal record. I tossed them both out to protect my babies. I suggest you give it some thought. She gets by with her behavior bc it is allowed by both of you. 

BTW, DH came back without her, housed her with his parents and she lived there making their lives miserable until she moved out. We are still married and after life dealt her a few blows that were nastier than her, she shaped up, became a decent human being and we get along quite well. 

Best chance, in my opinion is to make sure the girl is in therapy and get to the root of her issues.  Maybe they're with her bio mom?  Something certainly has her torn up inside, and maybe nothing will help, but it sounds like you've tried everything and need help from a professional.  I have a similar situation- a gf, her teenage son, me and my teenage daughter.  My gf's teenage son is pretty bad- he's been arrested for shoplifting, expelled from school, police have been to my house more than once due to his behavior.. very similar.  No easy answers but I believe therapy gives you and her the best shot of working things out.  If not, you need to decide if the heartache and conflict is worth staying in this relationship for you, and your son.

My BF's 13 year old daugher lives with us full time. She has been a MAJOR handful for the last year.  Her mother is not in the picture much at all (she has seen her mother only 3 times in the last 2 years).  We are also about to have a baby together (due in 3 months).  She has shouted at both of us about how this baby is ruining her life, how much she hates me, how I am not her mother. She loves that last comment. I am always thinking, "No I am not your mother, but your mother chose drugs over you and I am actually here trying to take care of your ungrateful butt!"  She has stolen pills, apparently is drinking (although we do not have any alcohol in the home), is saying hateful things to both me and her father (although her father just ignores her).  She is VERY disrespectful.  God forbid I ask her to do anything like put dishes up or take out the trash.  Her dad just ignores everything.  He has gotten to the point where he does not notice that either she or I even exist.  He does not discipline her at ALL and he never gets on to her when she is hateful to me.  I am sooooooo tired of it.  As much as I hate to leave when I am pregnant, I do not want my baby to grow up in this environment. 

It is REALLY hard being a parent in general...but being a step-parent to a teenage child who cannot stand you is WAY harder.  And then not having any support from the parent....tough! I feel for you and totally relate!!