Joliet police have arrested the girlfriend of a man suspected to have killed eight people Sunday and charged her with obstructing justice in the investigation of the shooting, which officials said cast a “reign of terror” over the southwestern suburb earlier this week. Police said Wednesday night that Kyleigh Cleveland-Singleton, 21, shared a 3-year-old son with alleged shooter Romeo Nance, 23, who died Monday night of a self-inflicted gunshot wound in Texas. Nance is allegedly shot seven of his relatives to death, police said in a news release posted to social media. Cleveland-Singleton and h…