How was Grace wrong in her assessment of her parents' marriage in the novel, You Should Have Known?

Marjorie Reinhart’s jewelry represents Grace’s incorrect assessment of her parents’ marriage. Grace had always believed that her parents had a happy marriage. She thought that her father picked out jewelry for her mother as symbols of his love for her. It was not until after Jonathan ran away that Grace learned from her father that her parents were never happy. He had given Marjorie the jewelry after he cheated on her and then decided he wanted to be taken back.