What is this “quiet war”?

Esperanza grew up in a neighborhood and household with different types of women. As an adolescent, this had an effect on her own self-image as a female. The "quiet war" mentioned in the book was Esperanza's initiative to not be like the girls and women around her.
The novel features vignettes, or sub-stories, featuring various female experiences. Some are even abused by their husbands, or are "imprisoned" in a life of domesticity. Additionally, Esperanza compared herself to "beautiful" people like Sally and Nenny. This showed Esperanza's developing identity in a neighborhood full of female identities to emulate.
However, instead of emulating them, she decides to go to "war" with these identities, and instead creates her own. The "quiet war" also illustrates that this conflict is internal, which shows Esperanza's rich inner-world and strong personality.