Oh and I compeletly believe there is such a thing as brainwashing a child. Children take in everything you say and believe what you say so if you are constantly talking negatively about someone then the children will think negatively about that person as well.
I completely agree with margypops. These are YOUR children not hers, and if she doesn't want to stick to the custody schedule that was set up in the courts you need to take her back to court and make it clear. I would suggest talking to her about it first, adn telling her that she hasn't been sticking to the custody terms and you want her to stick to the custody schedule and if not you will be forced to go back to court and let the court handle the situation.
I think you have to take this back to a court ,if you have filed contempt charges let the court make it clear to her. Dont concern at the presant the way the children behave, once you have them back with you ,you can clear up the misunderstandings, it is not the childrens fault, your daughter lives with them at presant her reaction is normal she has to live with them, you are her Mom that is the biggest bond, Let the court sort it out, they will be home soon, Good Luck