Sis said no to plus one at Xmas?

If people have met her already and liked her then I think there's no excuse. It's just mean to leave someone on their own if they don't want to be.
I suppose at least she can come to yours for the evening, which might actually be more relaxing for her (I personally find spending all day and evening around people tiring, whoever they are, and prefer shorter stints).

'Cold-hearted little cow', 'insufferable' - for saying no?
Never mind that OP only gave basic facts about the sister's response (there could be any amount of reasoning behind it), drop the hyberbole. You don't get to tell others what they are comfortable with.

There's not the point under discussion here.

Plus one is an odd description here. It's usually for weddings and events for someone to bring a date, or if not a good friend, as much because the invitee might not know other people there.

Including a friend who might otherwise be alone for Christmas is really kind, and I would always say yes, but a small family gathering is a totally different set of circumstances to a plus one type event and needs treating differently: checking in advance with the host and thinking about everyone's Christmas enjoyment.

Inviting them to your at home evening do seems like a good compromise,

Some people don't have a lot of money for Christmas dinner, for a start.

In my culture we bring people over without formal invitation. Sad that someone has to be alone.whats one more plate? Anyway not much you can do.

Tell them not to be so vulgar. Sheesh. You seem to have bred slobs.

What do you mean “ for whatever reason?”. The reason is crucial to this discussion!

Why did you speak to her before you checked with your family? You now have to tell her she can’t come which will make the family look bad but it’s your faux pas

Oh stop it don’t be ridiculous. Yes some people don’t have a lot of money, of course that’s true. No that doesn’t mean they have itemised their shopping to make one portion for one meal - Christmas always comes with tons of leftovers and a turkey will feed 7 just as well as it will feed 6. You’re just looking for reasons why it’s not doable.

YABU, sorry. While your impulse is generous, you should entertain this person yourself rather than imposing them on others.

Why do their feelings matter more than the feelings of your family?

Even in ‘A Christmas Carol’ Scrooge provided food and comfort to the Cratchitt family himself rather than expecting his nephew Fred to do it for him…

What do you think the ‘dynamics’ at Christmas should be if not showing kindness to others?

This thread is one of those MN threads that’s just mindblowing. Some people are so shallow. I had no idea. Do they think Christmas was invented purely for people to be able to post something to insta?

I personally wouldn't welcome a new person on Christmas day with children but it's lovely that you do. I think it's unreasonable of you to expect it of someone else but nice of you to offer.

Yabu. If you wish to be generous, then you can be generous with your own time/hosting/home. You cannot expect this from another family member. It’s not about how much food/space there is, it’s about family and privacy to me. Perhaps it isn’t to you, but people are different and your relatives clearly feel the same way as I do. I don’t want anyone random in my home as it’s my sanctuary.

And people in general are often cheeky pisstakers.

One year SIL brought a neighbour who was going to be alone on Xmas Day to MIL's
We soon found out why her family hadn't invited her to theirs
You can't invite someone to someone elses house without asking first and if they say no then its fair enough

I've always been of the thought the "more the merrier" so it wouldn't bother me but that said OP, a full day of family on Christmas day moving between houses is a lot for most people. You could have Christmas at home with your kids and family and then seen you sister another day over christmas.

Sorry, but you can't invite someone to an event (or part of an event) being hosted by someone else! Especially if they are expected to cater!

That's hardly the point.

It does change the dynamic. You shouldn’t have said anything before you asked your sister. Now it will be awkward for them to come in the evening, knowing they weren’t welcome at your sisters earlier. It would have been better to just invite them to yours for the evening do, then checked with sister about lunch and extended the invite if she was amenable.

I can see why dsis doesn’t want to change the dynamic for the main part of the day. You can’t relax properly, which in your own home is quite important.

Some people have more the merrier Christmases where anyone can pop along and pull up an ottoman to a coffee table and some people have ones that are more about relaxing in the company of their close family. I think what's gone wrong here is as you all contribute you OP consider this to be a joint enterprise where all the family are equal stakeholders whereas your sister sees it as you inviting someone she doesn't know well to a meal at her house.

Those people scraping by will have quite literally have itemised their shopping to make one portion for one meal.

Same. Not every year but we’ve had a few different people join us for Christmas dinner - one was a cousin, though not one I know well, but the others were friends/colleagues that we knew would otherwise be alone on Christmas Day and in most cases we’ve only found out they’d be alone on Christmas Eve, but we’ve still welcomed them in last minute. I love it but we’re otherwise a fairly small group of the same people we see daily/weekly anyway, so I find it makes it a bit more of an occasion somehow! I think it shows how insular we’ve all become, and how separated from our ‘neighbours’, that this is such a big deal to so many people.

Having said all that, you can’t invite someone round to someone else’s house, regardless of the event, without checking with them first. Even my husband checked with me first before inviting his colleague to join us, though he knew what the answer would be!

Most people would respond better to being asked rather than told.

What are you going to do? Stay at home with your friend and have your family over later as planned or go to your sister’s and have your friend to yours later?

We have a new person for Christmas most years as someone in the family as started a new relationship. The more the merrier its Christmas. We always have enough food to feed a small village. I tell people where the drinks are and to help themselves. So I'm not serving people all day. Its never been an issue Christmas is basically just a party and 99% of parties I don't know everyone there.

I want to feel 100% comfortable at my Christmas table. I want to feel at ease and enjoy quality family time.

I don’t want to spend it hosting someone I barely know.

I think your sister is very fair to suggest the evening is absolutely fine but the daytime is a no. You were reasonable to ask and now need to respect her answer.