Why does the mayor's wife not report Liesel for stealing the book from the fire?

The Mayor's wife 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.