Lying to Be Perfect (2010) on Netflix

Plot summary

Nola Devlin works as a magazine editor, where her coworkers overlook her and make jokes at her expense. On her own time, hidden behind a computer screen, she writes the advice column credited to Belinda Apple, a famous columnist no one ever sees. Her friends, worn down by long hours and unhappy with their weight, decide to form the Cinderella Pact and follow Belinda's tips to slim down together. Nola goes along with the plan, which means following the very advice she herself dispenses. Chip gives her a ride from the office, and they keep running into each other and become friends.