Answer:
Parvana's mother feels sad about seeing her daughter clothed with his dead brother's clothes. The clothes and the similarity of Parvana dressed as a boy reminded her of her lost son.
Step-by-step explanation:
Deborah Ellis' "The Breadwinner," tells the story of an Afghan family struggling to survive under the restrictions of the Taliban. The story's main protagonist is a young girl Parvana and how she had to take care of her family and keep them alive.
In the given excerpt, Parvana was dressed in her dead brother's clothes so that she will not be stopped by the Talib when going out to buy essentials. Once she's dressed in boy clothes, everyone including her younger sister couldn't quite figure out who she is. This means that her appearance changed with the clothes. And by the reaction of her mother who whispered "Hossain", it seems that she is reminded of her dead son.
So, we can infer that she feels sad when she saw Parvana in Hossain's clothes, and she might even think they look similar.