Q Dear Miss Abigail:
My uncle died last week and I just sent a sympathy card to his daughter. His daughter has two children (age 14 and 16) and I noted in the sympathy card that they were very lucky to have had such a great grandfather. However, I incorrectly called her children Amy and Ashley when it should have been Amy and Wesley. Should I let it go? Call her and apologize? Or should I banish myself? Feeling pretty stupid here. As a sidenote, this woman is throwing me a bridal shower on June 12. So, I know I will see her soon. Thanks in advance.
Signed,
Loser
A Dear Loser:
I’m sure the last thing your cousin is worried about is your erring ways. However, I do feel it would be appropriate for you to approach her with an apology. First, read the following tips from two etiquette books (the first by Margery Wilson, the second by Amy Vanderbilt). I’m sure they will help you get the courage to call or write; you will feel better, and I am sure your family will, too. And if this advice doesn’t help, please forgive me. I’m so sorry. Really, I am. I mean it.
1940: Apologies
Don’t apologize too abjectly, and don’t drag on with the matter of your fault or embarrassment. When an apology is necessary, give it quickly and easily. Cultivate the habit of saying ‘Sorry,’ in a nice, cool way when you are guilty of small offenses such as jostling someone. ‘I’m so sorry. Do forgive me!’ is enough for even the gravest offense. Apologize more readily than may be your wont, but keep it brief. 
Source: Wilson, Margery. The New Etiquette. New York: Frederick A. Stokes Company, 1940.
~ p. 200 ~
1967: Letters of Apology
Occasionally there is need to send a letter of apology. Such letters should really be notes explaining some remissness, such as the sudden canceling of a dinner or failure to keep an appointment, though telephoned or telegraphed word has probaby preceded the letter. Apologies of a more serious sort are difficult and sometimes useless to put in a letter. When some grave misunderstanding has arisen it is better, if possible, to settle it in person, as even the most carefully couched letter may merely add fat to the fire.
A note of apology need not be too definite. If you had sudden guests drop in the evening you had promised to play bridge with friends who were not near neighbors, you would write a note something like this if you had not been able to reach your hostess in person by phone:
Wednesday
Dear Carol,
Hope you received my message in time to get another couple for bridge Tuesday night. We had counted on it but had some guests from out-of-town show up unexpectedly just before dinner. Let’s try again for next week. Will you plan to come here? Please let me know.Love,
Ruth
Source: Vanderbilt, Amy. New Complete Book of Etiquette: Guide to Gracious Living. Garden City, N.J.: Doubleday & Company, Inc., 1967.
~ pp. 427-27 ~