My hubbys ex is using my step daughter

Doris • This is my first pregnancy. My husband and I are really exited! We are praying for a healthy baby.
My husbands ex wife loves to make us angry. She loves to try to piss us off at her 7 year old daughters expense. We have her 50% of the time and we are very concerned about her health because she is obese. Her mother (the ex) feeds her only processed junk food. She over feeds her pizza, cake, cookies ect. We are trying to get her use to eating healthy including vegetables and whole foods in her diet but her mother makes fun of it. "You are going to turn into a vegetable!"
She also smokes cigarettes in front of her and is very cheap; she doesn't buy her clothes and shoes.
The latest thing she did was chop off her gorgeous curly hair. She had the most beautiful hair that went down her back. Our step daughter said that she woke up at her moms house and it was cut up to her jaw line. His ex tried to blame it on us. I loved her hair! When I saw it was cut I cried. What can I do about this crazy woman??