Morgiana (1972)
Jealous of her vapidly "good" sister's popularity, poisonous Viktoria doses pretty Klara's tea with a slow-acting fatal substance. As the latter grows hysterically weak, the former finds success increasingly compromised by guilt, blackmail, and the pesky need to kill others lest she be exposed. jealousy, sibling relationship, based on novel or book, poison, inheritance
ETC.
