You need to file a Rule to Show Cause asking to find her in contempt of court and asking for legal fees, Hire a lawyer ASAP. If she repeated does this then you can ask for a change of custody based upon interference in the parent child relationship. That would ony be if the custody order is older than 2 years.
IF YOU FOUND THIS ANSWER "Helpful" or " The Best Answer" YOU CAN THANK ATTORNEY RADDATZ BY MARKING IT SO because Avvo awards the attorney points. MS. RADDATZ is donating her time and talent by answering questions to help those in need of legal information. This is NOT a consultation and in no way creates an attorney-client relationship. YOU SHOULD ALWAYS PERSONALLY CONSULT WITH AN ATTORNEY IN YOUR LOCAL AREA who has specific expertise in the area of law you are asking about.
You have rights. Out of curiosity, why are you just now getting around asking about which you can do about missed parenting time over Christmas? You should get copies of all your police reports and bring those, along with all of your court paperwork, to an experienced family law practitioner. It is past time for you to return to court on a Petition for Rule to Show Cause why your ex should not be held in indirect civil contempt of court for failure to comply with prior orders.