Dealing with an Emotionally damaged Stepdaughter
I am new here and desperate for any advice. My husband and I have 4 children. The two oldest from his previous relationship. The younger two are ours together. (Ages 6months, 5yrs, 7yrs, & 9yrs old). For a bit of a back story, my husband had had full custody of our oldest since he was an infant. Bio mom was pregnant at that time, but did not inform him because she knew he would gain custody once the baby was born. (Shes a REAL piece of work) She completely stopped contacting her son, and disappeared. Then one day he got a phone call from her that went something like "Oh by the way, you have a daughter, she's 4 months old" flash forward after a few years of her hiding from/evading him, and in result completely abandoning her son (no birthday cards, no phone calls, NOTHING) we recieved a court summons to claim custody of their daughter (who was now 4 years old) because bio mom was charged with felony child abuse and domestic battery. So thank GOD, after about a year of court hearings, home inspections etc, we recieved full custody of his daughter as well.
Now, I am, by technicality, the older children's stepmother, but I view myself as their mother because bio mom doesn't even TRY to contact them. She hasn't in over 2 years.
When my SD moved in I knew it was going to be hard. She had so far been raised in terrible conditions. So we loved hard and after about a year, you would have never known what a mess she had endured.
So my recent problem is with my dear SD, who seems to have regressed all of a sudden. She is 7 now, about to be 8. And it is as if she has COMPLETELY turned into a different child. She has absolutely zero respect for rules, animals, her siblings. She manipulates and finds joy in teaching our 5 year old to lie and bully others. If she is put in time out she screams, bangs her head against the wall, tries to hold her breath until she passes out. She is DEFINITELY exhibiting attention seeking behavior, but is only doing negative things to get attention. Screams that we're not her family, and she shouldn't be here...etc. (this will all be triggered by something as little as being told its not her turn to pick the kids movie)
My husband and I are pretty strict when it comes to respect, but we are pretty laid back fun people. We take the kids on adventures and whatnot all the time. I guess I need advice on how to handle this behavior, and thoughts on why all of a sudden she has regressed so drastically.
Thanks in advancr