DEAR MISS MANNERS: A “friend” of 25 years informed me over lunch in a restaurant that my husband of 39 years has been having a long-term affair with his assistant. When I politely told her that this was laughable, she really persisted, smirked, shook her head and called me naive.

There is absolutely no truth to what she said.

Do friends say things like this to friends? She says she was only trying to protect me. Do you believe this, and should I believe it?

Her husband of 30 years asked for a divorce four years ago, and since then she has been very bitter. She’s lucky to have some friends who took her under their wings and made excuses for her irrational behavior, but she doesn’t seem to be moving on, and the friends are starting to worry about her.

GENTLE READER: If you are asking whether it is an act of friendship to attempt poisoning a friend’s marriage, the answer is no. Not even if the would-be poisoner is miserable and wants company.

But Miss Manners gathers that you are not giving up on the friendship, tedious as it has apparently been for the last four years. You only want to squelch the accusation.

In that case, you should not be arguing. As you have already discovered, that sets you up for the trap of being “in denial.” Either way, you lose.

It is therefore time to be high-handed instead. “I’m sorry,” you must say coldly, “but I cannot allow you to insult my husband.”

Repeat as often as necessary.