וַיִּתֵּ֤ן לָבָן֙ לְרָחֵ֣ל בִּתּ֔וֹ אֶת־בִּלְהָ֖ה שִׁפְחָת֑וֹ לָ֖הּ לְשִׁפְחָֽה׃
라반이 또 그 여종 빌하를 그 딸 라헬에게 주어 시녀가 되게하매
Midrash Aggadah
"To her as a maidservant." And not to Jacob as a maidservant.
Pirkei DeRabbi Eliezer
(Laban) took his two handmaids, and gave them to his two daughters. Were they his handmaids? Were they not his daughters? But according to the law of the land the daughters of a man by his concubines are called handmaids, as it is said, "And Laban gave to Rachel his daughter Bilhah his handmaid to be her handmaid" (Gen. 29:29).