Planning her revenge
Seeing as Mr. Banks was an insurance salesman and Mrs. Banks a housewife, Sam soon realized they couldn’t afford to pay for their extravagant purchases and trips with their own money. As soon as she realized that, she made sure to write down every major purchase the couple has made, clearly using her money.
She never said anything to her foster parents, but waited patiently for the day she could use this knowledge and have their scam blow up in their faces.