Why does the mayor’s wife continue to allow Liesel to steal books?

Ilsa is a silent and mysterious woman who lives in sorrow over the death of her son. She takes a liking to Liesel and does not turn Liesel in for the political crime of stealing from a book burning, instead inviting Liesel to read from her massive library. It is unclear why the wife of a high ranking local political figure would act in this way, but the fact that her son froze to death at the end of World War I suggests that Ilsa, like Hans Hubermann, privately objects to Hitler and the Nazis' new war.