I wouldn't tell them because that's not any of my business & at the end of the day they might still be together. They're going to tell them who told them & it's just going to put me in an awkward position. So I will just let them find out on their own.
Most Helpful Guy
Personally, I think it is best to say out of other people's business, and just worry about your own. Like, how do you know what you saw was "cheating"? You don't know their business, and you shouldn't be prying your nose in where it doesn't belong. If you were ever to be wrong, that could be terrible for your relationship. However, I would never allow my friend to get hurt if I could knowingly stop it. May send an anonymous letter or something.0