You were confronting your cheating boyfriend (well ex boyfriend now) because he cheated on you with your sister, who was an angel. You were angry, but it was going to come anyway. You were a demon he was an angel. It was expected

Charlie, Angel Dust, Vaggie, Cherri Bomb, Sir Pentious, Husk and Niffty were listening in on the fight

Alastor was hidden in a closet in the same room, ready to protect you if your ex boyfriend were to hit you

Ex Boyfriend: SHE’S PRETTIER THAN YOU!! YOU’RE JUST A DEMON!!