it's not unreasonable, in a normal (non-toxic) family, to *want* to spend holidays together. THe older *I* get, and the busier we all are (siblings etc) (plus in our case it's living on different continents), the more I am happy to spend holidays or other times together. In fact, last week i spent two days (plus mucho $$ plus 6 hours round trip train ride) of passover at my very very religious sister's house - not my idea of a fun seder but the point to me was to spend time with family.
However, this is not a normal situation. Your MIL is being unreasonable (toxic). you are adults and you have the right to celebrate as you want - whether it's at home in your PJs or mountain climbing or whatnot.
SO i don't have any advice for you other than - if she wants to be angry, she'll be angry. that's her choice. you cannot control that.