What you need to look at is your passivity in the group, and is there a strong need to please others.
Our need for approval allows us to offer too much of ourselves to others, which they then can too easily decide to leave or take.
Because of low level of valuing yourself as a friend/group member, you take of the role of deferring to others needs before your own.
Here's a couple of clues
" They picked out the food (was taking pics and sending it on the group chat while they chose which ones they wanted) "
"we decided I'd host it"
What!!! how can 'we' decide something for YOU?
Read those sentences and see what role you are playing in the group.
(you went to great trouble to avoid making a decision and deferred to the higher powers because you wanted to please them.
Someone else might have said 'girls I'll just buy the usual stuff we like and you'll have to deal with that because I'm not spending ages trying to get agreement'.)
I suspect you rushed in to agree to hosting it because that serves a function for you being at the centre of things and being 'useful' because there's a part of you that is worried if you are not useful to people then what have you to offer them?
This dismisses and ignores the unique qualities you do have, that draws people to you. Because it's too scary to think people mightn't like you.
The more dominant others might take advantage of your willingness to be helpful. They would be thinking 'oh Susan won't mind if we postpone she's lovely and very easy going!'
In future, think carefully about your own time. No need to ditch the friend group, just take a hard and honest look at the role you play.
Then in future, think about what suits YOU. Don't think about how you can serve others.
A Sunday night (unlesss you are in Australia?) is not a great bet for an event.
Knowing how the group behaves, reduce your exposure to this sort of thing, by saying 'I might host it, but let's decide closer to the day, because I might change my mind'.
If someone make a request to you or a demand, the most useful tip is to buy time for yourself to think it over.
Simply say 'can I think about that and get back to you, not sure what I have on then'
Everyday of our lives is a learning day - unfortunately!