What did Wendy say to get the other girls to follow her actions?

Judy Blume's novel Blubber is a classic story about the power of bullies in a classroom. The main characters are Jill, Linda, Wendy, Tracy, and Caroline. They are students in a fifth-grade class. They are all students in Mrs. Minish's class, except for Tracy. Mrs. Minish is described as a strict, no-nonsense teacher—perhaps one who doesn't even enjoy teaching or being around young students very much. Tracy is in a different class, with a teacher who appears to be fun and innovating.
Jill is the protagonist of the story. She is friendly with Wendy, Caroline, and Tracy. In the story, Wendy is portrayed as a popular and smart student who is good friends with Caroline. One morning, a student named Linda is giving a presentation about whales. When she gives facts about whale blubber, it prompts Wendy to write a note to Jill and Caroline that states "Blubber is a good name for her," due to Linda being somewhat heavy-set. The note makes its way around the classroom, and soon Linda is the target of class bullying.
The girls follow Wendy's lead because she is so popular and mean. At one point, Jill helps Wendy bully Linda in the bathroom during Halloween and is not afraid of facing any consequences. She knows that Wendy will not get in trouble, because no one tells on her out of fear.
The tables turn on Jill after she is made fun of by Linda at a party that is outside of school. Wendy is amused by others getting hurt, and so she is now good friends with Linda—turning the classmates against Jill. Wendy gives Jill the name "Baby Brennar," with Brennar being Jill's last name. Jokes about Jill not being potty-trained and needing diapers ensue.
In the end, Jill is able to fight back, and she sees that Tracy is a good friend who did not get caught up in Wendy's world. Wendy has moved on to other friends but continues to be a bully who has not learned any lessons. In fact, she fights with Caroline, who was once her sidekick and good friend. The reader can infer that Caroline will soon become a target of Wendy's bullying.
Wendy is a strong character. She motivates people out of fear. It is only after Jill experiences the bullying herself that she decides she may want to make changes in her own actions.