Complex sentence: Mirella Gregori (born October 7,1967) mysteriously disappeared from Rome in May 1983, about 40 days before the disappearance of Emanuela Orlandi, a citizen of Vatican City.
Split into simpler sentences: Mirella Gregori (born October 7,1967) mysteriously disappeared from Rome in May 1983, about 40 days before another girl's disappearance. The other girl was Emanuela Orlandi, a citizen of Vatican City.