I am in search of answers for my 12 yr old. Maybe someone will have some ideas for me.

For starters, she was an only child until she was 8. She was spoiled at that time. I got pregnant when she was 7. I explained things like all attention wont be on you etc. I know at 7 it didnt sink in completely. The father of the children was an alcoholic. I finally got the courage to make him leave around her 9th birthday. She never seemed overly excited about her brother but accepted him mostly. Over the last few years we have moved in with my boyfriend. She has become aggressive with brother, hateful to me and my boyfriend. She seems totally dissatisfied unless there is something in the situation that will benefit her. She lies about EVERYTHING, she has tantrums like a toddler and completely defies authority unless it benefits her. She is driving me crazy and I need help. I took her to her doctor who diagnosed her ADD and as having anxiety. He put her on medicine but none of it seems to help and her grades are still horrible as is the disrespect at home. She isnt disrespectful other places like she is at home. WHAT CAN I DO BEFORE I GO NUTS?