Dear sister,

When our mother goes out of her way to make a dish that you can eat, what with your allergies and other dietary restrictions, for your birthday, it’s generally polite to show up for dinner on time, if not slightly early. 

Dinner was at seven o’clock. 

That doesn’t mean you can show up at eight thirty. Without phoning, no less.

Sincerely,

Your sister who thinks you’re horribly ungrateful.