What is Wiesel's final image of his mother, and where was she going?

In chapter 3 of Night, Eliezer and the other prisoners arrive at Birkenau, the reception center for the notorious Auschwitz death camp. Upon arrival, the prisoners are split up into groups: men to the left, women to the right. This means that Eliezer is immediately separated from his mother and sisters. He catches a quick glimpse of them as they are moved away to the right. Eliezer's mother is stroking his sister's fair hair; it's almost as if she's trying to protect her daughter at such a deeply traumatic moment. In reality, there is little she can do. Like everyone else in the camp, they're completely at the mercy of the Germans. Eliezer doesn't know it yet, but this is the last time he will ever see his mother and sisters.