The way I was told the story (and remember it), her father and her older brother Alfred fled, leaving her mother, herself and her two sisters alone.
Sonia, her mother and her sisters apparently were on the move a lot for a while (until 1943 it seems). As I understand it, they were later caught and sent to a camp.
My grandmother never really used that term however, and certainly didn't expand on it. She'd usually say they were "sent to work".