I have three daughters, all adults now with their own children.
My wife and I made it a rule never to get involved in spats either between them, but especially not between them and their friends.
The dynamics of relationships between females of any age is complex and constantly shifting.
I understand that you want to do the right thing here, and teach your daughter the right thing as well, but honestly, stay out of it.
You are putting your adult perspctive of right and wrong behaviour onto individuals who are still figuring out what that actually means, and you may cause more harm than good doing it.
As you point out, the relationships shift on a daily basis - that's what girls do, and they are much better left to work it out for shemslves.
If you make your daughter miss the party to make a point that you think is right, and she and more importantly her friends, will not understand or appreciate, you are damaging the ecosystem of the friendship.
Yes for right reasons, from your point of view - but damage is damage, whatever the reasons behind it.
If your daughter wants to go, let her, and you will find that this rift will be forgotten in a day or so, and something else will be there in its place.
When your daughter talks about her friendships, listen always, but refrain from offering your input.
She is not talking to get a judgement from you, she is talking so she can put her thoughts in order, and work out what she thinks - today, because tomorrow she will think something different.
Leave it alone - you shouldn't get dragged into situations you don't really understand, and can't alter for the better, much as you would like to.