3 year old out of control

We adopted McKinnzie at birth. She was different from the start,I have six of my own children so we have been around children. She is very strong willed, mean to other children, screams, hurts animals, Life with her is always a struggle. She is a live wire, by the end of the day we are so tired and drained. She so pretty and sweet when she wants to be. She does not like change, or to be with strangers. If we go out she keeps saying I want to go home. If are asked to go to someones home she will cry while we are their, like she is scared. I used to go to church but I cant go now. She also is in speech class, I have spoken with the doctors and they just say she is 3. But I feel its much more. We love her so much, we need help to help her!  Karen