My question involves a child custody case from the State of: Illinois

My husbands ex-wife has been staying within the lines of the paperwork that they agreed to 6 years ago during their divorce. Now that she has remarried they are not letting him have his 9 year old daughter for the last half on the Christmas break. We used to live in Cincinnati and she let her stay with us the entire time because she works full time but this year she would prefer her to be in daycare or with her relatives. Is the paperwork just suggested and anything better for both parents and the child OK or are they just plan suggestions that can be broken if someone wishes.