When my kids went off to university, it was always understood that they could decide how they wanted to spend their holidays. Mostly, they came home but sometimes they spent part of the holiday elsewhere. At that age, I think they are somewhere between childhood and adulthood, and part of making that transition is learning to make your own decisions and plans, while also taking family and friends into consideration. That's not always easy, even as adults, but you have to gain experience in order to learn.
I committed to putting my kids through four years of higher education to the best of my financial ability. That commitment was meant to be "no strings attached" with the exception of expecting them to maintain their grades. It was not a business contract, as in, I pay and that gives me the right to make all your decisions for you.
And when you equate spending time with family to chores, well, then it becomes a chore rather than a pleasant choice. I never want my kids to think of spending time with me as a chore or obligation. I want them to think of it as a pleasure.
So, as you can surmise, I'm on the side of Jessica. John needs to realize that his baby is growing up and he needs to begin to let go. The more tightly he holds on, the more Jessica will try to break the bonds. And at some point, when she is no longer financially dependent, there's a good chance she'll bolt.
One question I have: Before Jessica made (or at least announced) her plans, did John make any effort to include Jessica's boyfriend in their holiday plans? Did they invite him, even if not for Christmas day, to spend at least a part of his holiday with them?