How and why does the narrator attend a support group ?

Hazel is suffering with cancer. She is depressed because of her illness, as well as the knowledge that her condition is uncurable. Because of Hazel's depression, her mother talks to one of her many doctors and gets her set up with antidepressants and a regularly meeting support group for youths with cancer.

Hazel sarcastically describes Indianapolis as America's 137th nicest city give another example of her ironic tone and explain how it enhances her character