There is no way to tell why she wants to go except that in MLC they do the opposite of what they did or felt pre-crisis. It could be that she wants to take the kids there to show her parents that she's a good mother and everything is okay or it could be that she wants to revisit her youth through the eyes of her children...but whatever the reason...she's the only one that may be able to shed some light on it.
Is there any way to compromise? Is she planning to be there the entire holiday? Is there any way that one of you can have the children a few days before Christmas Day or right after that day? This is one of the areas where
At some point, the two of you will need to set up a schedule so that you both know when you are having the children on certain holidays. One year, you have them on Christmas and the next year, she does.
I'm very sorry that things aren't turning out the way that you had hoped...but you still have a few week until Christmas and anything can happen between now and then.
Sit quietly, the answers will reveal themselves when you least expect them to. The past is gone, the present is a gift and you need to focus on today, allow the future to reveal itself when it is ready.