I think they must have updated traits and more drama in this game if that is happening. I have a sim couple who won't stop fighting with each other. They both have the evil trait plus she/Juliet is High Maintenance/Self Absorbed/Erratic/Snob. I used the more CAS traits mod to have that many traits. Juliet seems to be the one initiating these fights. It's a bit frustrating though. I wish there was a way to have evil people get along with each other while being nasty to everybody else. They are both evil soulmates after all!