Sister is Weird about Christmas & Doesn't Like Her Family

Hithere

I am afraid you have answered your own question

"Ever since I can remember, she didn't want much to do with our parents or me, starting in her early teens. She just hated spending time with us. "

So your sister likes spending Christmas the same she grew up, may I ask why does it surprise you this much?

She clearly showed her preferences early in, which are the opposite of yours.

I do hope you enjoy Xmas this year and in future years as well.
I would stop having unreasonable and unrealistic expectations on your sister

It's true, but I just don't get it. Our parents did so much for us, and they loved her and their grandchildren so much. I'm just disturbed by how awful she can be and that she's never matured out of it.

This is my first Christmas with no parents and I also got divorced this year. She begrudgingly said she would have me if I had nowhere else to go, but she's been very clear about how much she detests seeing her family at Christmas. I'm spending it with a friend.

You can't change her.
Enjoy your Christmas with your friend, someone who actually wants your company.
I can't think of much worse than going to your sister's under the circumstances you describe.
You say you get on well the rest of the year so see her then.

Karma might catch up with your sister in years to come; her own children might have families of their own and choose to follow her example and not invite her to their houses 🤷

It's true, but I just don't get it. Our parents did so much for us.

My 2 sons and their families get along well and meet up often. But my daughter is not part of their group. Admittedly, she is older than her sisters-in-law , by roughly 10 years, and she is teetotal, so not much fun I guess.. If it wasn’t for me, we wouldn’t have a family Xmas. I am organising a family lunch in the NY.
Family dynamics are more apparent at times like these. Hithere says, just enjoy your xmas, whatever you do.
However, I do feel sorry for your parents.

I agree with Hithere. You can't change her now and she probably knows you resent the way she treated your parents.
At least you can see her at other times of the year.

Christmas can be a difficult time for so many for various reasons. All the expectations to be jolly and sociable when that's not how you feel.

I hope you enjoy your time with your friend.

My bil is like your sister , they spend Christmas Day with just my sister and their two ac . They won’t travel to visit me or our mother . We’re a 2 hour from them and I can’t remember the last time we spent Christmas as a family.
My bil has never had a close relationship with his parents or sister . I’ve realised that family just isn’t important to him , apart from his wife, my sister and their ac.
Maybe op , your sister is the same.

I am afraid you have answered your own question

"Ever since I can remember, she didn't want much to do with our parents or me, starting in her early teens. She just hated spending time with us. "

So your sister likes spending Christmas the same she grew up, may I ask why does it surprise you this much?

She clearly showed her preferences early in, which are the opposite of yours.

I do hope you enjoy Xmas this year and in future years as well.
I would stop having unreasonable and unrealistic expectations on your sister