Background. Have a very pushy sister, we both have young children similar ages. We see each other once a week with our youngest kids (joint child activity). For the rest of my free time I spend with my little family and go with the flow (happy with a pj day if required!), but if she ever has a spare day e.g. at a weekend/school hols when her friends aren't around, she will ring/text endlessly and If we dont meet up with her she's rude and pissy and insists her children are "left out" or "upset" as a result (never seen anything to suggest this). She's well off compared to us and makes suggestions for day trips that are ££ and politely I don't want to spend every weekend entertaining her children - she will happily sit on her bum and let me mind all the kids. She's extremely talkative compared to me which is fine, that's her, but it's A LOT in long doses tbh.
Anyway, every Christmas she insists on family get togethers against my parents wishes. Every single day of the holidays she has to be at someone's house for food/sleepover to the point she's not in her own at all, from Christmas eve til the kids return to school. Mum has expressed repeatedly she's had enough hosting everyone at once now we have so many kids between us in a small house and when COVID hit, it obviously all stopped and they preferred it. We now go as separate family units on one separate day each. However, every single year sis will arrange a date, and then nag nag nag until mum (who gets upset every year) eventually caves and hosts her for new year to gap fill until she returns home. I have stayed out of it and for the past couple of years happily go with my little family one day but will not impose on the "joint" get together and turn it down. But as a result get an endlessly hard time for weeks for "not making an effort for family at Christmas" am asked to justify why I don't want to go: followed by a barrage of photos of their get together. Aibu to continue to turn down these invites down? Conscious parents aren't getting younger but feel like I'm being bullied and badgered constantly and quite frankly enjoy shutting the door on it all for a few days for some head space (as I said, I see her weekly) and just let my kids lounge in their pjs etc.
And yes, it's obviously frustrating for me that parents "write rules" and then cave to her but when I say she's persistent, she's effin persistent (will result to grandchild blackmail if required).