So if OP's mom is anything like my grandma (and I suspect she might be), here's how I see the scene playing out.
... mom and who says "What are you talking about Region? You do the cookies every year! Oh the little ones were so looking forward to it, how could you not bring the cookie stuff?", at which point Region blinks...didn't she? Wasn't there a conversation about? "Mom, you said in our talk about the rules, you didn't want Santa cookies this year. Remember, we couldn't bring our dog, we better not wear shorts, and no cookies?", which will get a "What are you talking about. I never said any such thing! You didn't bring the dog? But my little precious was so looking forward to playing with your dog! And now there are no cookies for Santa either?" ...
The technical term is "gaslighting". It's common in toxic people.
No kidding. After my grandparents died my mother would make a big point that there were NO gifts being exchanged when we went to visit her sisters at her parents home. It was because aunts just didn't make as much, there wasn't enough money. I told her "Well I'm making earrings from what I have at home, it's no trouble or cost to me so it really wouldn't be an issue at all.
"WE'RE NOT EXCHANGING GIFTS!"
We get there and you guessed it, not only are they exchanging gifts but my mother clearly had knowledge of it because she's pulling out gifts for them that they've picked out for each other ahead of time. DH, the boys and I even got gifts from my aunts and here we are with nothing to exchange for what we were given.
They weren't pricey gifts at all, but very nice ones, like one aunt took a beautiful picture of my grandparent's pier at sunset and framed it. Another year she gave us framed photos of our oldest two that were very nice.
Me: Tell me what you bought for Aunts and I'll make something pretty to go with it.
Mom gave me a look like I had amnesia: What? I didn't buy them anything, we're not exchanging gifts!
Me: Uh-huh. Seriously, what did you get them?* I'd like to give them something this year and I'm sure they'd like something to go with whatever you bought. *the gifts were always clothes and my aunts are jewelry wearers*
Mom: I did NOT buy them anything this year, we swore we weren't going to do it.
Yeah, stupid me, I fell for it...they exchanged gifts. The year after that was after the CD but I was SO relieved not to have to play that game again.
*Yeah, I know the response was rude, I was just that annoyed.
Oh and my mother's response? "Oh well those presents don't count! We went shopping together and as a joke we just grabbed something off each other's stack of purchases and bought it for them for Christmas!"
Yeah, Ma, that's a gift.