Finch's eighteen-year-old sister is a caretaker of sorts. She's in charge of the cooking, making a batch of casseroles at the start of each week. Finch tells us:
Kate offered to stay home [from college] when the divorce happened. Someone needs to look after Mom, she said. (8.31)
At the end of the day, though, she's a teenager—and a little bit of a delinquent one, at that. She poses as Finch's mom whenever someone from his school calls. She secretly smokes and is rarely home for long. She tries to look after Finch, but sometimes her "help" does more harm than good.