Why does Frankie end her relationship with Rye in the book, The Women: A Novel?

Initially, Frankie refuses to enter into a relationship with Rye because he is engaged. Eventually he tells her that he is no longer with his finance, and they begin a romantic relationship while on R&R. While Frankie loves Rye, he proves that he is unworthy of her love numerous times. The first way he proves this is when he lies to her about breaking off his engagement when in reality, he did not. She does not learn about this until he returns from being a POW. Then when the two again enter into a relationship while he is married, he tells her that he will leave his wife, but later Frankie learns that his wife has just given birth meaning that she was pregnant with Rye’s baby during the time he was telling Frankie he would leave his wife. After this, Frankie pushes Rye out of her life.