What major step does Amal take in Chapter 14 and who gloats about their role in Amal's decision?

In Chapter 14, after all of her friends, but particularly Adam, encourage Amal to sign her name on the list of debate participants, she finally decides to do so. Amal waits until the end of the school day, when she knows no one is in homeroom, and she writes her name on the debate participation list.