AITA for saying she's not my bio daughter if she doesn't want to live with us?

I (40m) got my youngest daughter Narissa (17f) from foster care, when she was three. I had two older daughters (20f, 19f) with my late wife, Gabrielle. She passed away when our youngest was eight. I have three daughters now, the three I mentioned.<br><br>My oldest daughters are teenage tendencious, and are overall not very fond of Narissa. I have three boys I'm mentoring as well. The oldest of which (14m) has been very sweet to Narissa.<br><br>The other two are hellhounds. The thirteen year old makes fun of Narissa nonstop. And the sixteen year old, Sarah, is just as bad.<br><br>Narissa is very fond of both of them. And doesn't really like Sarah much at all.<br><br>I've tried to address it multiple times. I spoke with Sarah about her behavior, and Sarah mentioned she hates Narissa because she's so young, and doesn't want her around the house. I told her if she didn't like it, she could move out. And she agreed to let Narissa live with me and my new wife, Karen.<br><br>That was three months ago. Sarah has been doing everything in her power to make sure Narissa feels unwelcome. The entire house is off limits, unless Narissa is going to her room or to the bathroom. Even though there is plenty of space, Narissa has to share a room with Sarah until she can get her own. And she gags Narissa with spicy food. Sarah even asked me once if we could consider adopting her, over Narissa. And I told her yes, but that means she has to be willing to act like a mother.<br><br>Yesterday, I had discussion with my daughters. And Narissa said she didn't consider Sarah her bio mother. And Sarah got upset. And I supported her. I talked to Karen about it, and she supported me. And now Sarah is running her mouth about how she's going to go into the state foster care system, and no one else will want her. And she made me realize, the only way she knows is to make Narissa suffer, is to leave. So AITA?