Why does Nadira seek her sister out at school in Section 7: Chapter 9? Where do they go after school?

Nadira feels lonely because she is worried about Abba, and she finds Aisha in the cafeteria, realizing her sister is the only one who will understand, and suggests maybe they can figure this out together. After school, the girls go to Dunkin Donuts where Aisha tries calling the INS but receives the runaround.