My friend revealed that she hooked up with someone we went to high school with. That someone is currently dating another person we went to high school with. My friend asked if he had cheated before that and he said yes with 2 other women. I told her someone needs to tell his girlfriend that he's cheating on her, and she said she doesn't want to. I definitely don't think I should personally get involved but I can't stand back, knowing this girl is being cheated on and do nothing.