What does Phoebe lecture the Finneys about?

(Walk Two Moons)

When Sal and Phoebe arrive at the Finneys for supper, the house is bursting with activity. The boys are playing, Mary Lou's sister is on the phone, and Mr. Finney is doggedly cooking in the kitchen. When they sit down to dinner, Phoebe expresses shock that the Finneys are serving fried chicken, explaining the dangers of cholesterol to the entire table. She refuses every dish handed to her on the basis of its fat content. Eventually, Mrs. Finney grimly presents the finicky girl with a bowl of muesli.