The Wail in Spring 1981 on netflix

Princess Geumsung desires after General Kim Mu-young and plots to destroy his family. She buys off his house servant and charges his wife Bo-ok of debauchery and drives her out. She also poisons his two children, Jin-young and Jin-sik. Bo-ok, who has lost everything, becomes a fox and starts taking vengeance. Once she has had her revenge, she dies in the arms of her beloved husband. General Kim realizes his foolishness and enters mountains with his wife’s body.