What was the source of Rachel's jealousy of her sister Leah?
Rashi: She was jealous of her good deeds. 1 Had her sister not been more righteous than her, she would not have merited children.
Tosfos ha'Shalem (1) #1: The words of her sister, "My husband will accompany me" (29:34) aroused her jealousy.
Tosfos ha'Shalem (1) #2 (from Bereishis Rabah 71:6): she thought, because Leah married Yaakov first, she merited children - and this was because I gave to her the Simanim!
Malbim: She understood that Hashgachah causes the hated wife to bear children. It is better that I be the one to be hated, and bear children!
Gur Aryeh: How do we know to explain this way? G-d forbid that such a righteous woman would be jealous [of something transient]; for jealousy removes a person from the world (Avos 4:21).
Did Rachel 'blame' Yaakov for her inability to have children?
Rashi (from Bereishis Rabah 71:6): Yes. She claimed that Yaakov ought to have prayed for her, 1 in the same way as his father Yitzchak had prayed for his mother Rivkah (25:21).
What do we learn from Rachel's statement, "v'Im Ayin, Mesah Anochi"?
Ramban: What she meant was that, if Hashem does not give her children, she will die out of distress (in the way that women tend to exaggerate their pain).
Tosfos ha'Shalem (1) #1: For whom will I long and get delight from?!
Tosfos ha'Shalem (1) #2: Who will mention me after my death?
Tosfos ha'Shalem (#2): Due to these words, she died when giving birth to Binyamin. 3
Ha'amek Davar: Sometimes a woman wants children for pleasure - for this, her husband can appease her through extra affection - "Anochi Tov Lach ma'Asarah Banim" (Shmuel I 1:8). 4 He makes a meal and appeases her (Nedarim 90b). If she wants a son to support her in her old age and to bury her, there is no appeasement in place of this. Rachel said, Misah is written about one who dies without Banim (Bava Basra 116a), for no one mentions them after death.
Tosfos ha'Shalem (6) supports this from Chanah's words, "Hashem Memis u'Mechayeh" - i.e. He gave to me children, and revived me.
The curse of a Chacham is fulfilled, even if it was conditional and the Tenai was not fulfilled (Makos 11a). Perhaps this is why she died at the first moment that she was not destined to bear more children (PF).
Ha'amek Davar: Chanah vowed that if Hashem gives to her a son, she will give him to the Mishkan, to show that she did not intend for pleasure.
Why does it say that she did not bear children "l'Yaakov"?
Ohr ha'Chayim #1: Yaakov already fathered children, so he is not sterile. She must be the one who is sterile!
Ohr ha'Chayim #2: He is a great Tzadik, so her lack of children is due to him.
Malbim: She attributed her lack of children to him. Scientists say that excessive love sometimes prevents bearing children. Or, Hashgachah causes the hated wife to bear children.
Ha'amek Davar: She thought that he did not merit children from her. Even though he had children from Leah, Rachel was his primary wife. If so, he did not merit, and he should be Moser Nefesh to do something to merit [children from her].
Why does it say that she was jealous "b'Achosah"?
Ohr ha'Chayim: Sisters normally have similar natures. Had a stranger given birth, she could attribute this to her nature.
Malbim: Yaakov already fathered children, so he is not sterile. She must be sterile!
QUESTIONS ON RASHI
Rashi writes: "From here we learn that one who is childless is considered as if dead." Why is this so?
Gur Aryeh: 'Life' means without cease or pause; just as a flowing spring is called a 'Be'er Mayim Chayim.' Death is pause and cessation. If a person lacks children, there is a pause in his continuity.