Oh dear at your MIL. It sounds like that although she has officially relinquished responsibility for Christmas she still wants to be in charge of it and wants to make sure that they have a very traditional Christmas in terms of what her family has always done, or rather how she has always done it.
I think you will just have to let some things go and some things you need to take advantage of. For example, I would probably ring up at beginning of December (or email!) and say "What did you say you are bringing again?" and make sure she brings as much as possible so that the load is off you.
![Big Grin :D :D](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
Add your own side dishes etc that you want to add, that is part of YOUR Christmas tradition, they can eat it or not - it's their choice! And if she wants jelly to be layered in a certain way, she can jolly well do it.
It does not matter if she has not done it for altruistic reasons, the main thing is that some of the burden is off you. You do NOT want to get more ill over the whole Christmas affair.
At the end of the day, it's about giving his family a warm welcome but making sure you look after yourself too. If things don't go to plan in her eyes, then that's HER expectations, not yours and don't let that upset you. If things don't go to plan in your eyes, drink some more.
And remember, Christmas is not Christmas unless someone has a tantrum or a cry. Just make sure it is not you by taking a deep breath, taking it easy and taking offer of help.
Do I sound harsh? I don't mean to be.
![Stick Out Tongue :p :p](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)