Answer:
Towards the end of the book 'Speak', Melinda is stuck in the closet with 'IT'. She takes a piece of the broken mirror and holds it up to his throat with the words: "I said no." This seems to be one of the most stark examples of irony from the book.
Step-by-step explanation:
The said situation seems to be ironical because since the start, her own self image hasn't been very good, and it is the mirror itself which has represented the same. Since she never liked looking at herself, she would always cover all the mirrors. But now, the tables have turned - Melinda is emotionally stronger with a sense of self. Hence she holds up the mirror to Andy's throat, to prevent him from abusing or hurting her once again. This seems to be quite ironical.