Lillian becomes engaged to a wealthy banker in Chicago and asks Annie to be her maid of honor. At the engagement party, Annie meets her fellow bridesmaids: Lillian's cynical cousin Rita (Wendi McLendon-Covey), idealistic friend Becca (Ellie Kemper), raunchy future sister-in-law Megan (Melissa McCarthy) and Helen (Rose Byrne), the beautiful but vain wife of Lillian's fiancée's boss. Helen and Annie are immediately jealous of the other's friendship with Lillian, but Lillian persuades them to spend time together. During a game of doubles tennis, Annie and Helen are hyper-competitive, deliberately hitting each other with their volleys multiple times.
Annie takes Lillian and the bridesmaids to a Brazilian restaurant for lunch before going to a chic bridal gown studio. While Lillian is in the restroom, Annie suggests a Parisian-themed bridal shower, but Helen thinks this is a bad idea. At the bridal gown studio, Helen uses her influence to gain them access because Annie did not realize that reservations were needed. However, everyone except Helen (who did not eat the meat) becomes ill with food poisoning. While everyone else becomes ill, Helen orders for everyone the bridesmaids dress that she liked the best.
