Blokova refers to a prisoner who has been tasked with managing other prisoners. Typically, blokovas were non-Jewish prisoners. This is a tenuous position to have. On one hand, it grants a small degree of privilege compared to the other prisoners. On the other hand, blokovas are often the first to receive blame and punishment if something goes wrong in the prison block that they manage.
Hannah's blokova is having a hard time managing her prisoners. She does what she can to ensure discipline, such as confiscating Hannah's blue ribbons. Yet, her missing fingers are signs that she is not always in control. In chapter 16, readers learn that she lost her first finger as the result of a riot sometime before Hannah's arrival. Her second lost finger was her punishment when several of her prisoners hanged themselves one night. She loses a third finger as a result of the failed escape attempt of Yitzchak and Shmuel. There is certainly no love between the prisoners and the blokovas. They often have the power to choose who lives and who dies, and Hannah and the other girls speak derisively about their overseer in low tones.
Yet, the elevated position of the blokovas means that they are often privy to certain information that the other prisoners are not. For instance, it is the blokova who informs Hannah that Marta and Renata were being moved to another subcamp.