It is rude to tell everyone about private messages.
Sally gets a private text message from her husband while she is visiting her friend.
Sally wants to make conversation with her friend.
Sally talks to her friend about topics of mutual interest but doesn't bring up the text.
Sally tells her friend what her husband wrote to her in the private text message.
Sally's husband asks her if she told her friend about his text and is happy when she says she didn't.
Sally's husband is upset when he finds out that she told her friend about what was meant to be a private matter.