How do I tell my friend that I slept with her fiancé?

I didn’t know they were together when it happened; I met him online and we had a one-night stand. I found out the next week that he was the guy she was engaged to. What should I do? — L.K., New York

It’s a lot cheaper to cancel a wedding than go through a divorce. Your friend may never speak to you again, but you should tell her, especially if you’re in the bridal party. When you tell her, be prepared with evidence — like his online cheating profile and the messages he sent — and some good running shoes in case she goes berserk.

But know this: you didn’t do anything wrong. There’s no reason you can’t hook up with people from the Internet.

However, if you met him on a website that caters to people who are already in relationships and looking for something on the side, you don’t get to say anything. Ever.

You knew what you were getting into, and he has every right to believe that you will keep things quiet.

This column doesn’t constitute medical or professional advice. Always consult a qualified health care professional for your medical, psychological, or relationship problems.