Why did Lavan send his daughter Rachel to shepherd the sheep and not regular shepherds?
Targum Yonasan: Lavan's flocks were struck by a plague and most of his sheep died. The few sheep that remained 1 he gave to his daughter Rachel to look after.
Refer to 29:6:152:3.
Ohr ha'Chayim: "Ha'Tzon Asher l'Aviha" implies that this was his entire flock.
Why did Lavan make Rachel the shepherd, and not Leah?
Ramban #1: He did not appoint Leah to look after his flocks, since her eyes were 'tender', and the sun 1 would have caused them damage.
Ramban #2: Because Leah was older and fit to get married, and he was concerned for her safety. 2
Chizkuni: This was to honor her older sister.
Tosfos ha'Shalem (28:8): Leah was more beautiful than Rachel. Lavan hid her in inner rooms.
Seforno, ha'Emek Davar: Rachel was knowledgeable in the art of shepherding. Ohr ha'Chayim
Chizkuni: The wind and air would damage her eyes.
Ramban: Yisro did appoint all his daughters shepherdesses, either because due to his high position, he was not worried that the men would molest them, or because the family of Avraham were intrinsically more modest. (The shepherds repelled Yisro's daughters! Why it is more modest to send one girl alone? Some permit a man to be alone with many women, unless his job involves women (Rema EH 22:5)! (PF)
Why must the Torah say that Rachel is a shepherd? This is obvious. She was coming with the flock!
Moshav Zekenim: It teaches that even though she was a shepherd and in the heat of the sun, which blackens, she was beautiful.
Seforno: This teaches that she was knowledgeable in the art of shepherding.
Malbim: This teaches that Lavan had a small flock when Yakov arrived. One small girl was able to watch all of it! Ohr ha'Chayim - "ha'Tzon Asher l'Aviha" implies that this was his entire flock.
Ohr ha'Chayim: Do not say that she was coming because her nature was to go out. No, it is because she was a shepherd.
One might have thought that she was not a shepherd, and due to Hashgachah Pratis, today she tended the flock! Refer to 24:15:151:1. (PF)
Why does it say that Yakov was speaking with them? They were the last to talk when Rachel came!
Ohr ha'Chayim #1: The entire episode is to teach what happened with Yakov, therefore it is said from his perspective.
Ohr ha'Chayim #2: Really, she came before they answered him. The Torah first gave the dialogue, and then says that she came when he was talking.