Picture Mommy Dead (1966)

Teenage Susan Shelley is released from an asylum where she's been confined after the shock she suffered from her glamorous socialite mother Jessica's fiery death. Her father has a new wife, who has only married him for the money Jessica left him. Susan is still haunted by her mother's memory, and her stepmother is conspiring with her lover, Maxwell Reed, to trick the troubled girl into leading them to Jessica's missing diamond necklace.