Well, the dad did try to rape Eurngjun in the past. That's why May is so crazy. Jealousy made her kill Eurngjun. After killing her, May should've just let her go and not condemn her to never be born again. That's just cruel. So, Eurngjun killing everyone off is fair, since she can't be reborn as of right now. When she died, she also didn't know that her boyfriend didn't accept the marriage to Dao. She died thinking he was marrying someone else. So, I wonder if that's why the bracelet can hurt her.