Or HaChaim on Genesis 29:29/אור החיים על בראשית כ״ט:כ״ט

1 לה לשפחה. as a maidservant for her. The Torah was careful to add the word לה, as I have already explained in connection with verse 24.

2Alternatively, Laban made a condition that Jacob should not have any claim on Bilhah; we find in chapter 22 of Maimonides' Hilchot Ishut that if someone gives a wife a gift with the proviso that her husband should not have any claim on that gift, then the husband is not permitted to enjoy the "fruits" of such a gift (in this case Bilhah's labour, etc,). It is a principle of our sages to follow a line of exegesis which puts Laban in a bad light.