At what point do you break up a couple?

My sim Evan Straud (son of Vlad and Evie Delgado) proposed to his gf, Morgana Rasoya FOUR times and one of those times, he actually did it autonomously (thanks to MCCC) but the silly girl kept turning him down. So I got fed up and had him break up with her. His twin sister, Scarlett married a townie and I moved him in, but somehow, she kept flirting autonomously with Salim Benali's son whenever they were in a club gathering. So I took drastic measures and had the hubby *accidentally* get struck by lightning and he died. Few days later, I had Ricardo Benali move in as a 'roommate with benefits'