What can I do if the mother of the child is not following court order papers?

My fiance has a 3 1/2 yr old daughter. We live in Louisiana but they live in MS. They have joint custody and he's suppose to get the baby every other week end and every other holiday, and 2 weeks in June and 2 weeks in July. The mother has only let the baby come about 7 week ends all together in the past 2 1/2 years, no holidays and no summer vacations. She says the papers mean nothing, unless it's to do with the child support. She still wants my fiance and will call and text him and when he tells her he's not going back to her, she will hold the baby against him. He drives the whole way to pick the baby up and drop her off when ever he does get her. The mother will not even meet at a local store, much less half way. She has also slapped him in the face and hit him before, in front of the child. What should we do to make her realise she can't keep the child from her father???