I told a strangers fiance he was cheating
Why would you interfere with their relationship?
I wanted to be nice. I wanted her to know what he did behind her back so she could be the one to decide if she wanted to stay with him.
I understand you just wanted to help, but it's best to just leave their relationship to themselves and your own to yourself. You might have misunderstood what was going on, which could create unnecessary tension for them.
It's her life and she can do whatever she wants.
Exactly, I know that you were just trying to help. I just think that it is wrong to get involved in other people's relationships.