She's a complete whore, I can't stand her. I feel sorry for the guy he deserves way better! I know it's not my place or business, but she's such a slut wheeling along the poor guys that she meets, giving them her viruses.
If yes, how do I tell him?
Most Helpful Guy
First, you try to convince your sister to come out. Tell her she has to do it within, say, a week.
If that amount of time passes and she doesn't do it, tell her boyfriend. But make sure you don't let your sister know that you're gonna tell on her. When you ask her to come clean, make no indication that it's a threat.1
Most Helpful Girl
Ever consider writting an anonymous or presenting some type of evidence that's hard to deny instead of just telling?
You don't have to tell him she's cheating but maybe write something like ''meet her at 4pm (the hour she's cheating for example), I heard there was gonna be some party or something''.1