SOLVED. True story about a guy and girl over 10 years, including 9/11

[Liz]

SOLVED. I confirmed with my mother-in-law that it is The Girl He Used to Know. (My mother-in-law read this book about a year ago that was promoted on her Libby app.)

A guy and a girl meet and begin dating (in college?), but they eventually break up. The girl tells most if not all of the book. It covers 10 years of time. The meet again later. The guy was injured in 9/11. The girl had a mental disorder of some type. It is based on a true story, but I do not know if it is classified as fiction or nonfiction. Part of the story takes place in Chicago too.