Hope things work out well for your mom, Andy. Maybe that's why she overreacted. Not like she hasn't been going through a stressful time.
I'm 30 years old and opening clothes is still boring AF. If your 7 year old niece apologized for being bratty, the one time your mom/her grandma had ever seen her be bratty, she's gotta be a pretty good kid. Hopefully it'll all blow over soon.
It's hard as things change over the years and it always sinks in on holidays, but you find new traditions. This was probably the best Christmas I've had in a long time, and that's without any grandparents left, and my brother's also gone. We adopted my grandma's best friend as "grandma", so it was her, my parents, my sister, my husband, and the kiddo. We still don't see my in laws due to their crazy, so my husband is a bit stressed about that on holidays. He's the only child, and the only family he is close to (some cousins) live in Florida. He has no family at holidays of his own, just my family (and our daughter of course), but he still said it was the best Christmas.