YANBU to want Christmas your way.
YABU to tell her to bog off. Don't stoop to her level.
You want to be considered an adult? That means and you have to act like one. It took me 30 years of feeling pathetic, guilty, ashamed, lazy, selfish and all the other things my narcissist mother piled on me since birth to realise this. BE THE ADULT YOU ARE.
Tell her, I whatever way is most comfortable FOR YOU that coming over Christmas Day isn't an option this year. No need to explain, justify, massage her ego, make her feel OK - not your job.
"I know you want to come over but this year you'll need to make other plans. I am going to be blissfully avoiding Christmas Day. A lie in, not cooking, not looking after children, not managing the Christmas mayhem. I'm going to be in front of the TV catching up on everything I've wanted to watch all year with a bacon sarnie, oblivious to the Christmas Shenanigans.
The children will be back on x. If you want to come over late evening and spend some time with the the next day before heading back home., let me know. If not, we'll see you in the new year"
I have to manage this every year. We take it in turns to host (3 siblings). When it's my turn, we get an Airbnb nearby. I will not have her in my house. This year we agreed we needed a break so we each contacted her (I texted) months in advance to say that this year we had different plans for Christmas so to sort herself out. I will miss being with my siblings but they don't have the courage to do a Christmas together without her. We would never ever be allowed to forget it. Ever.
Sadly, one of my siblings caved just a few weeks ago and our mum will be with them. I felt guilty for a millisecond and then realised - they made that choice.
What I realised, 20 years too late, is that this type of person (makes no difference that they're your parent really) will never change and will make you feel sh#t whatever you do, so you may as well do what makes you happy. The consequences are the same...
Good luck