'Mistress' in the Bible

He went in to Hagar, and she conceived. When she saw that she had conceived, her mistress was despised in her eyes.

He said, "Hagar, Sarai's handmaid, where did you come from? Where are you going?" She said, "I am fleeing from the face of my mistress Sarai."

The angel of Yahweh said to her, "Return to your mistress, and submit yourself under her hands."