I met my DH 9 years ago and we got married a couple years later. He has 2 daughters who are now 17 and 16 and I have 2 bios who are 17 and 15. I know, 4 teenagers right!!!  I believe at first my dh and I were naive in that we thought we could blend a family. I did not know what I was up against as far as BM went at all. She was unmedicated with huge mental health issues, had disowned a teenage son from another marriage,  and a completely horrible person. She started drilling into these girls heads that they should hate me, my kids weren't blood so they weren't family, there dad was a horrible person who hated them, etc as soon as I was in the picture. My DH spent almost 10 years in/out of court fighting her. Ultimately, because she never changed her ways, he was granted majority custody with the girls going to visit her twice a month. He was completely involved in their school, after school activities, shopping with them, etc. and we ended up with 3 out of our 4 kids are going to have the ability to graduate high school early. Meanwhile, the PAS sets in with my sd17 even though she only sees bm twice a month. Over the years, we had escalating very dramatic negative behavior. It starts with the whole "youre not my mom" thing, bm sends home 26 diaries for sd to write everything she hates about me in, then in 8th grade sd17 decides she wants to be anorexic, starts researching it online, we put a stop to it,(she was in counselling for years through all of this), in 9th grade she joins the cross country team at age 14 and has sex at bm's house with one of the 18 year olds on the team. (bm has no rules at her house, lets guys spend the night). then we find out she has had sex with multiple people. A couple months later she throws the fake rape card and accuses an invisible person of raping her at homecoming football game. we contact police and they pull up the camera footage and...nothing. the police confront her, she admits she lied. we have the juvy officer come to the house for 6 months to "scare her straight". she manipulates juvy officer into thinking she's on track. After that, it's minor things like fake injuries so she has to wear an ankle brace and wears it for 4 months, latching on to her younger sister and saying she needs her for emotional support, starts saying that she has anxiety and needs to come home from school, we continue with her counselling. Then she starts to have angry outbursts and continually goes to the school counselor for sympathy. She decides to tell the counselor that she "might" be suicidal. DH takes her to the hospital and they admit her for a week, then send her home with 6 months of intensive outpatient therapy. She uses absolutely zero tools that they teach her. She is switched around on 8 different medications and continues seeing a psychiatrist and counselor. Meanwhile other sd winds up pregnant at bm's house and has her baby , so her attention can no longer be on her sister. SD17 becomes more and more outwardly hostile to me and spews filth daily in emails to dh while she is at school. Then she starts threatening to move back to bm's house and go off her meds and not go to college. At 17, my dh and I are now exhausted by all of her antics. He lays it out to her that  she has 2 paths to choose from. One will take her to college and help her be successful and the other will not. She has a chiropractor appointment for fake jaw pain and my DH asks me to take her since he has work. I stupidly say sure. The day of the appointment she comes stomping downstairs all angry and I ignore it and take her to the appointment. At the chiropractors, he asks about her mental health. She tells him she has outbursts 5 times a day. he tells her that means she has underlying issues that she needs to confront and use tools to deal with. She doesn't like that answer apparently. I take her to school and she emails DH making up a bunch of lies, saying i'm a horrible person, mentally abusive, etc. then she tells dh she isn't coming home and goes to bm's house. Ive watched this girl go from a semi decent person to completely downhill over her high school career. This is what happens when the other parent brainwashes a child so thoroughly. She texted other sd last week and said she was coming to get her stuff, other sd told her she needed to come when dh was home. she didn't come that day. then she finally met up with dh and he basically told her that this path was her to choose, that he loved her and hoped that someday she would see the choices that she has made. she told him she's going off her meds and not going to school. We also find out she and bm have been planning this and she was basically looking to cause a big blowout so she could be ignorant and throw it in his face .  I  was her primary target which is why the blatant open hositility. I have told DH that whenever she is here picking up items, he needs to be here. I don't trust her, I think she's dangerous. He agreed.  I have never seen someone so able to create so much drama. Literally everything is turned into drama of some sort. She can't just ... be.    Today as I sit here writing this 1.5 weeks after her moving out, I am sad yet relieved. I am sad that we lost this battle and that my husband who has his children's best interest at heart was treated so horrendously by this girl who acts so terrible. I am sad because it does feel like a piece of our family is missing. Yet, I am relieved that I no longer have to walk around wondering when she will lash out again and I can relax in my own home and enjoy life. And then I feel guilty for feeling this.