what does mama change her mind about in chapter 3 los hijos

Tío Luis once again offers to marry Mama and promises to build her a bigger, more beautiful home. He threatens Mama and she reluctantly relents, much to everyone’s surprise. However, Mama decides that she and Esperanza will accompany Hortensia, Alfonso, and Miguel to the United States. She explains that she has only agreed to marry Tío Luis in order to buy some time.