Most Helpful Girl
This responsibility does not lie on your back.
It lies on hers to do the right thing.
Imagine, if you did tell and she denied what you were saying.
Your friend would not know who to believe.
It's very possible, that he may even believe her over you.
Then who is made to be the bad guy?
Sometimes doing what is right, can get you into a deep hole.
You have to weigh your options on this one, and go from there.
Ask yourself, "Does the bad outweigh the good?"
I say yes.
More negative effects can come from you telling the truth than good.
If you're willing to take that chance, then be out with the truth to your friend.
Most Helpful Guy
i would tell the cheater that they need to come clean... if not i may have to tell the cheatee