So you’ve caught your best friend’s boyfriend cheating, which could mean you saw him and the girl holding hands or being intimate, or they were just simply talking. Whichever the case, what is the right thing to do? confront the boyfriend and the chick, call your friend up and tell her what you saw, or mind your own business?
In my opinion, I would first confront the guy, then tell my best friend. Ladies remember that is your bff, and you should always have her back and keep her best interests at heart. If you mind your business and deny what you saw, your bff will be subdued to a period of heartache, not to mention she’ll be upset if she finds out that you knew something and said nothing.
By keeping it to yourself will affect your friendship; everytime you meet or hang out with your bff, you’ll feel guilty about not saying anything. But what if the boyfriend wasn’t cheating, what if it was just a friend? well then I would suggest confronting him, but then again he could deny it as well, saying it really is just a friend. So if you do approach him, just observe his reaction: if he looks utterly surprised and looks like he’s putting words together in his mind, he’s obviously cheating or just worried you got the wrong idea. Maybe paying keen attention to the girl as well will tell you the truth: if she looks really embarrassed after he dismisses her as “just a friend”, then something else is going on. If you’re worried about telling your friend then maybe you could write her a letter (like what the girls did for Sammi on Jersey Shore..lol jk).
What if you tell your bff and she doesn’t believe you? Oh well, you tried, and after telling her what you saw, the only thing that’s left is for her to confront her boyfriend about it. In the end, if he really was cheating, she’ll come to you (her bff) for comfort, or if he wasn’t cheating, you both can still make up if she was upset before.
This is just my perspective. What do you think?
EMBRACE YOU 
Here is an article I wrote on the cheating http://loveengineer.com/4460/cheating-relationships-stats-men-women/ with hard stats. 40% of people cheat in their relationships men or women. I find people who cheat are selfish and have taken their other half’s for granted. I don’t believe we can abolish cheating, but hope both parties can work threw it and do what is best, either reconcile or breakup without hostility. From my own experience I have learned once a cheater always a cheater, even if they have done lots of counseling, have realized their mistakes, felt bad for what they did and say never again I hurt too many people. I learned the hard way if they don’t cheat sexually they will emotionally or both. It always comes down to them enjoying forbidden fruit, it is like a drug to them.
@Love Engineer,
I disagree with you on the notion that cheating is “like a drug to them”. I am not in any way condoning cheating, but sometimes shit happens that was not pre-planned! Good points though, thanks for stopping by. Hope to see more of your comments around!