...because you didn't actually invite this person in the first place, but they incorrectly assumed that you would be sending them an invite.
Do you...
A.) Say nothing about it to this person but quietly send invites out to the people who *are* on your list?
B.) Try to find a polite way to break the news to this person that they aren't on the list.
C.) Start a fight with them so that they wouldn't want to come, anyway.
D.) Something else dramatic, or not.