Is this machine translation with little to no quality check? some part just doesn't make sense, the child shown is also clearly a boy and not a girl.
The book mentions that she is a girl, I quote you the literal text of the chapter (called “Mama, What's a papa?” chapter 6 of the original work) where his short interview is narrated:
«I went back to my village…Children are playing outside our house. I look and think: “Which one is mine?” They all look alike. Shorn as sheep used to be—in rows. I didn’t recognize my daughter and asked which one was Lusya. And I saw one of the kids in a long shirt up and run into the house. It was hard to tell who was a girl and who was a boy because of their clothing. I asked again, “So which one of you is Lusya?”».
I understand that the mangaka's representation here was taking into account the slums of that time, the few resources that families had to support their children/grandchildren and obviously the plagues of lice.
But that's what I understood, don't pay too much attention haha.... Good luck, thanks for commenting!