I do send a little fault Lita's way. It sounds like she cancelled at the last minute. That cancellation, I'll fault her for. BUT...
OP, I don't fault her family for wanting to see her on Christmas. If they came across the country to see her for the holiday, they are perfectly within their rights to include Christmas. I live across the country from my parents and brother and if I weren't invited to, say, my brother's girlfriend's house for Christmas and they went, I'd be hurt. Even for four hours. Because really, it sounds like quite the project to get all of the siblings and their families together. You don't know what went into making this trip. Heck, it's hard enough for just me to arrange to visit.
As for dinner, it sounds like this is the real point of contention. Not only did Lita (perhaps understandably) cancel, but you sound more peeved about getting stuck with Chinese food. Did you consider checking on places that are open on Christmas, where you could get a more traditional take-out? Even a Denny's could have boxed up some meals. Also, many grocery stores (not mine, unfortunately) are open for awhile on Christmas, so picking up some potatoes, a bag of frozen veggies, packaged stuffing and maybe a turkey breast or some Cornish hens would have been possible.
If I were you, I would have made the best of it, dumplings, Szechuan shrimp and all, and made sure your grandmother had a grand time visiting with you. As for your Dad, it sounds like he was disappointed with Lita and he should be the one to address it with her.
In short, I can definitely see where you were annoyed, and this could have been handled better, but don't make it a hill to die on. If Lita is still in picture next year, you're forewarned.
Oh--one more thing. Chinese on Christmas is quite common and not just a "Jewish thing." Think A Christmas Story.
In fact, as someone who spent Christmas Eve and Christmas Day alone this year (save for my faithful little bunny) I would have been quite happy to have company, even if we had Chinese. Which I actually did. Both nights. And it was deee-lish.