Don't interject yourself into the romantic relations of others.
Karen sees her best friends's boyfriend talking with another girl.
Karen wants to be a good friend.
Karen thinks there must be a reason for him talking to another girl and minds her own business.
Karen thinks her best friend's boyfriend is flirting with the girl and calls her best friend right away to inform her.
Karen finds out that the friend's boyfriend was just talking to his sister and doesn't cause problems in her friend's relationship.
Karen's best friend screams and yells at her boyfriend and their relationship is damaged.