No where to turn

This is my first post so I will give some background. I have two adopted children (one step (10) , one not (12) and a biological 16 mo old.The two adopted children were in contact with their bio mom up until three years or so and ultimately her rights were terminated due to multiple failed reunification attempts. We ultimately adopted my stepdaughters oldest sister who has adjusted well after therapy and is very much attached to the family. The 10 y/o has been in counseling since the age of 4 when she was first removed from her mothers care and since then we have been given a number of diagnosis for her and after 6 years in therapy, including family therapy which was a disaster, with no hope of knowing what is really going on with her. ODD was her first diagnosis, then ADD was pursued but she fell short one point on the assessment for the diagnosis, then PTSD. All of her symptoms seem to fit under RAD and her new therapist believes this could be what she has though because of her age it is difficult to pinpoint what is going on with her. She's had trauma, abandonment, and 100% sure there was substance abuse during pregnancy. Her behaviors started worse in the home, mostly towards me her stepmother, and she seemed to be doing well in school though she had some issues. Now her behavior at school is resulting in suspensions. She lies, steals, destroys property, runs away, approaches strangers, sexually aggressive, and has some self harming behaviors. She fears no authority, has no sense of danger, and presents no empathy when she hurts others. We've re homed two pets and have had to limit her time around her other siblings because of her violence towards them. I am to the point that I feel hopeless and am just waiting for CPS to show up at my door which would make me lose my job because well...i'm a social worker! I've read books, been to countless therapy sessions, even went as far as calling the local police department the last time she stole an item and was told I could not be helped because they did not want to make her scared of the police! I've spoken with the principal and am told she's not as bad as the other kids so she isn't on their radar with her behavior. Yet I have parents coming to my home because my child is a bully or stealing their items and she's getting kicked of the bus. So I feel I am just having to sit and wait for it all to explode in my face and lose my other children because I have no other place to go with my fears. How am I supposed to care for my children when one child is destroying the whole family? And sadly it makes me regret the adoption all together then I feel like a horrible person. My marriage is in shambles because of this, my mental health is deteriorating, and I dread going home. It makes me feel like a monster to feel this way.