Who is Gerda's best friend as noted in the memoir, All But My Life?

Ilse is Gerda's best friend through their ordeal after the Germans invaded Poland and took over their town of Bielitz. They are transferred from one women's camp to another. The war is nearing its end when the girls are forced to work for months to evade the emerging allied troops. Ilse is too weak to keep walking and dies from exhaustion, illness, and exposure.