Email 1: School secretary, to whole school
Remember everybody, if you’re going to the holiday party, you need to RSVP as soon as possible.
Email 2: Me, to school secretary
I’ll be there!
Email 3: School secretary, to me
1 or 2?
Email 4: Me, to school secretary
1, but thanks for rubbing it in.
It’s nice to know that being single and attending a party alone is such an unthinkable state of affairs that it can’t be inferred by the simple lack of mention of a plus one, but must be explicitly mentioned.