I'm not sure that it is always worth telling them. Some people are implying that you'd have nothing to lose. Well, maybe that's true in your situation. But such thing can ruin friendships; and, making it public would mean that, say she started dating someone else, it would be harder to bare than if you'd kept it private because of the extra humiliation.

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"The less people know about how sausages and laws are made, the better they'll sleep at night".
- Otto von Bismarck