I'm not the woman in question - but it's entirely possible that someone could see me that way.
I strongly suspect I'm autistic, although haven't had a formal diagnosis.
In this scenario what would happen for me is:
We would get the invitation, and I would absolutely say yes. I am an introvert, but a social one, and I enjoy being around people (for a while. I have a limit).
The day would come, and I would be feeling good about it.
I would get there and suddenly be faced with a lot of people that I don't know well, all at once. And they would be having a big group conversation - and I can't cope with that. I can't think quickly enough to join in, as there's so many voices and it's overwhelming. So I would sit feeling awkward and out off place, and sometimes use my phone as a distraction from feeling uncomfortable - in part because I don't want anyone else to feel awkward because I'm not joining in. Sometimes I'll just sit and listen, and smile/laugh where appropriate.
Don't get me wrong, it doesn't always go like that. If it did, I would never go. If the big group is broken up into smaller groups, then I love to get to know people, and happily chat away, in twos or threes. Family groups though, are usually the hardest to be in, because everyone knows each other so well that the chat involves so many people and often people will be having more than one conversation at once.
I have been described as a snobby cow and a stuck up bitch. I'm really not.
I'm not looking for sympathy or to make this about me. And I don't know if the woman in question's experiences are anyone like mine. But maybe this might help others understand a little of how big group occasions can be for some people.