Esther, a Jew in a society that was very anti-Jewish and persecutory, risked her life by revealing her ethnicity to the king and asking him to rescind a proclamation to exterminate all Jews, which he did. The celebration that followed is recognized annually today as the the Feast of Purim, still celebrated by Jews today.
Though very likely a fictional story (dates, names, even the historicity of the events don’t add up) all of Scripture is true “for the sake of our salvation.” (CCC 107-110.) A timeless truth of Esther is that we must speak out, even to government when our faith is under attack. Don’t hide your Catholicism!
Catholic Doctrine Bible Study