Esther keeps her Jewish background secret (Esth 2:19-2:21)

“Meanwhile Mordecai was serving in the courtyard. Esther had not disclosed her kindred or her people because Mordecai had instructed her not to do so. She was to fear God and keep his laws, just as she had done when she was with him. Esther did not change her mode of life.”

The Greek text is more religious than the Hebrew text as it says here that Esther feared God and kept his laws, so that she did not change her mode of life. The Hebrew text simply says that she did not reveal her origins.