‘Young & the Restless’ Star Kristoff St. John Dead at 52, Fiancee Distraught

8:50 AM PT — Kristoff’s fiancée, model Kseniya Mikhaleva, reacted to his death, saying … “How did it happen??? How??? Why did you leave so early???? and left me all alone …” Kristoff and Kseniya just got engaged 5 months…