Final answer:
The misquoted idiom from 'Daughter of Invention' that conveys Laura's indifference towards a person is 'She's just like one of her father's portraits. They never interested me. Nor does she.'
Step-by-step explanation:
The misquoted idiom from 'Daughter of Invention' that is intended to mean that it makes no difference to Laura is: 'Well, is that anything against her? She's just like one of her father's portraits. They never interested me. Nor does she.' In this context, Laura is implying that the person being discussed is of no importance or significance to her, just like her father's portraits that never interested her.