Why does the narrator most likely mention the story about her friend dying father

Probably because this is a important turn of events inside this book. Her friends father might've been close to them, or family to them. Either way its important because this character was most likley close to the main character's heart AND because its a friend, it brings a major turn of events, but it also gives the main character a something to reflect on and how to get over it.

Explanation:

its repetition emphasizing that the chain is his own. sorry if i am wrong.