How does Tris use verbal irony on page 318?

Verbal irony involves saying what you don't mean or the opposite of what is true.... you say one thing and mean another. An example of verbal irony would be something you accidently do wrong.... possibly spilling something all over the floor, and an ensuing exclamation of "GREAT!" It isn't great, you're being sarcastic...... 

I do not have the text of Divergent here at home with me, but you're looking for an instance where Tris uses sarcasm. 

why does tris use sarcasm