Answer: If the friend is a close friend, you certainly want to let her know. Do it gently, and in private. Say something along the lines of, “I am going to tell you something I would want you to tell me … you probably want to find a breath mint because your breath is strong.” Let her know you often have the same problem after a spicy meal, and emphasize that if the roles were reversed, you would certainly appreciate the same kindness and respect.
It’s all about being diplomatic, courteous and to the point. The alternative is to let her go on with her day smelling like a bowl of French Onion soup.