In the novel In The Time of the Butterflies, how does Patria change throughout the book?

In my opinion, Patricia is the character that goes through the most dramatic changes in the novel. Patricia changes from religious, to being in love, to losing a child, to losing her faith, to regaining her faith on a pilgrimage, to being a devoted mother, to being a committed member of the movement against Trujillo.

While quite young, Patricia is entranced by the nuns and the religiosity of their Roman Catholic faith.  She longs to be one of them.  Of course, this is where young love enters the scene and, at the tender age of sixteen, Patricia falls in love with Pedrito González while she washes his feet in the context of the ritual washing during Holy Week in the Roman Catholic Church.  They quickly marry and have two children.  However, when Patricia's third child dies, she loses her faith and doesn't regain it until going on a religious pilgrimage.  Patricia becomes a devoted mother through this time and worries about her children, especially when they become involved in the movement against Trujillo.  Patricia makes another transition when she moves the meetings of the movement from "near" her home to "in" her home.  This puts the family at risk.  Patricia is eventually killed as a result of her devotion to the movement.

Patricia's journey, then, is a complex one that involves religion, motherhood, and politics.  Here is a quotation from Alvarez that is important to remember in the context of this journey:

A novel is not, after all, a historical document, but a way to travel through the human heart.