DEAR MISS MANNERS: I am having a birthday party, and my sister-in-law wants to bring her friend whose birthday is the same night as mine. Is it rude of me to say no?
GENTLE READER: No, but Miss Manners recommends doing so on the basis of acquaintance (specifically, lack thereof) rather than competition. And once you explain that you are inviting only your friends, you had better do so.
(Please send your questions to Miss Manners at her website, www.missmanners.com; to her email, dearmissmanners@gmail.com; or through postal mail to Miss Manners, Andrews McMeel Syndication, 1130 Walnut St., Kansas City, MO 64106.)