The Time Traveler's Wife
by Audrey Niffenegger
Celia is a friend of Ingrid, Henry's ex-girlfriend. Clare meets her for the first time during a concert at the Aragon, shortly after she witnesses an argument between Henry and Ingrid. Henry tells Ingrid that he won't come back to her. Celia, on the other hand, warns Clare that Henry is Ingrid's business and that she should just stay away from him because he's bad news.
Henry claims that Celia is in love with Ingrid. His claim turns out to be true. When Celia finds out that Clare is engaged to Henry, she persuades Clare to meet her and Ingrid at a bar. When Ingrid notices Clare's engagement ring, she accuses Celia of using Clare to show her that Henry is gone for good.