Genesis 16:4

ויבא אל הגר ותהר AND HE CAME UNTO HAGAR AND SHE CONCEIVED from the first union (Genesis Rabbah 45:4). ותקל גברתה בעיניה HER MISTRESS WAS SLIGHTED IN HER EYES — She said, “As regards this woman Sarai, her conduct in private can certainly not be like that in public: she pretends to be a righteous woman, but she cannot really be righteous since all these years she has not been privileged to have children, whilst I have had that blessing from the first union” (Genesis Rabbah 45:4).

וַיָּבֹ֥א אֶל־הָגָ֖ר וַתַּ֑הַר וַתֵּ֙רֶא֙ כִּ֣י הָרָ֔תָה וַתֵּקַ֥ל גְּבִרְתָּ֖הּ בְּעֵינֶֽיהָ׃

And he went in to Hagar, and she conceived: and when she saw that she had conceived, her mistress was despised in her eyes.