My daughter hasn't ARGUED anything. She hasn't even SPOKEN to dad. She ASKED dad to call her to talk about it. And I believe that it is well within her rights to ask to talk to Dad about something, ANYTHING that's bothering her.
Dad hasn't had the common courtesy to answer her calls.
This has really gotten off the issue of your initial question and on to the issue of parenting, and everybody has different opinions on that.
I do feel strongly that once children reach a certain maturity level that a parent is obligated to listen to their concerns, and is obligated to give the children sound reasons why their concerns cannot be addressed (if they truly cannot be addressed) the way that the children want them addressed.
Now, if its just a teen who is bored a dad's house (for example) then a sound reason can simply be "because, whether you are bored or not, its important that you spend time with your father. You may not agree with that now, but you will understand it later". Then, if the teen refuses to accept that, then it can end up something along the lines of "well, you are just going to have to deal with it".
However, in a situation like this one, where dad has told the children about the court orders and happily let the court orders be disobeyed (and in fact asked the children to ask to you allow them to be disobeyed) for a holiday that benefitted him, but won't give a little on another holiday because it doesn't benefit him, he is sending the wrong message to his children...particularly a teen who is old enough to understand the inequity and has a strong opinion about it.
I said that dad was an AZZ because he doesn't understand the message that he is sending to his children, and doesn't realize that they are getting old enough to form their own opinions and that those opinions will carry on into their adult lives, and to their adult relationship with him.
He could easily give a little in this situation...even if that "give" was only a few hours. However, he may be being stubborn because some extended family of his planned their Christmas celebration for later on Christmas Day, because that was how they did it the year before.
I do however think that you should take this situation back to court. Each of you should be getting 1/2 of the children's Christmas Break from school. There should be no such thing as "regular weekends" during Christmas Break. If you each get 1/2 of Christmas break that allows enough time to accomodate all extended family, even if that means celebrating Christmas on a non-traditional day.
So...you get an order that states (for example) that you get the first 1/2 of Christmas break in even years, and dad gets the last 1/2 in even years, and then it flips in odd years. Whoever doesn't have Christmas Day fall in their 1/2 of the break, gets noon on Christmas Day to 8AM on the 26th. That eliminates the entire problem, and makes things fair for everyone, including the children.