Why is Nooria becoming nicer to Parvana?

I'm not sure exactly where you are in the text, but the love that exists between Nooria and Parvana is unquestionable. They may fight, as sisters often do, and their may occasionally be a level of jealousy on both their parts. Nooria, however, is justifiably concerned for her sister's welfare and understands the danger in which she places herself daily. This concern is blatantly evident when Parvana goes to the prison with her mother.