8 Year old daughter defiant, violent and we are at a loss

I dont know what to do about my daughter. She is 8, and extremely bright. She has also had some special needs, due to an less developed part of her brain. She excels at school and we hear she is nice to be around. We get compliments from her teacher and principal about how great she is, and how curious she is about the world. For this, we are very proud of her.However, at home, my wife and I feel like prisoners in our own home. I am actually her stepfather, and I have been raising her since she was 2. She goes to her dads and stepmothers house for 48 hrs every other week. Actually, due to recent behavior, they now only take her for 8 hours every other week, because she is "too much to handle."She will say how much she loves you and cares for you if she is doing something she wants, like making pancakes or doing crafts. If you ask her to do something involving getting ready for school, getting dressed, brushing her hair, etc, she completely changes, like flipping a switch.She turns physically and verbally abusive. She screams she hates us, she wishes we werent alive. She tells us she wants to live at her dads. When that doesnt get her way, she resorts to violence. Hitting, kicking, throwing things. Destroying our things. We dont give in to what she wants, but she keeps it up anyway. She says she wants to punish us for not giving her her way. We have a system of incentives and consequences and we remind her of this, but she chooses the bad choice 99 times out of 100. We remain calm as much as we can, which is probably 80% of the time. We never hit her, but if she is being unsafe and destructive I carry her to her room to serve out her consequence, while being pummelled the whole time. If she comes out and fights with us again, I carry her back. Sometimes I hold the door shut and just keep reminding her of the consequences and the choices she is making. Its exhausting, frustrating and depressing. It can go on for hours. We tell her all the time we love her, even when its hard to do so. Sometimes we just try to do nice things for her just to get some reciprocal love before it goes to shit again.She goes to a counselor, and has been for a year. She has been diagnosed with anxiety, and bordline ODD (no official diagnosis). She is on concerta and fluoxetine, which havent done anything. Her counselor says she is making progress, but none of it has translated to home.She has been hit by her father and stepmom, but apparently not enough for CPS to investigate as it didnt leave marks. She has told us her stepmom screams at her and spanks her over and over while her dad watches. At her dads, everything has been taken from her room except her bed, until she can "be respectful." In fact, when she misbehaves to that level, he bails and drops her off to either us or his sister, reinforcing the behavior.My wife blames herself for all of this, because its her child. I dont know what to do. I dont usually resort to telling strangers my problems, but our life is falling apart. I'm sorry, and I hope you have a nice thanksgiving. She is with her dad for a few hours, so we are trying to regain some sanity and see some family before it starts again. via /r/Parenting https://ift.tt/2DTHE06