You are at the supermarket car park loading your shopping from the trolley into your car. You notice your best friend in another car not far away with a man. You do not recognise the car; nor the man she is with. It's certainly not her husband.
Suddenly, she is embrassing the man passionately. It is very obvious this is not just a friendly kiss; but something more serious.
Do you just look the other way and drive off ignoring what you saw?
Do you speak to her about it at some other time?
Do you tell her husband?
Or do you comfront her there and then about cheating on her spouse?
What else would you do?