She had lost her position as first wife, and then she had heard the sounds from the bridal tent—laughter and muffled cries of pleasure. (1.2.51)
Not only does Rachel lose her position in the family, but she was also duped by Zilpah about what sex is like. Naturally, this precipitates a nasty form of jealousy that never really disappears.
Rachel was furious when she learned that Leah was with child. (1.2.58)
So, to go along with Rachel's jealousy regarding Leah's marriage, the resulting child then ticks her off even more. It's sister-rivalry in the making.
I suppose it only natural to assume that Leah was always jealous of Rachel. And it was true that Leah did not sing or smile much during Jacob's week with Rachel. (1.2.61)
Though Rachel was always jealous of Leah for marrying Jacob first and bearing him his first child, Leah was always jealous of Rachel for being blessed with great beauty. See, it goes both ways. But we can't be too surprised: as Bronze-Age women, all Leah and Rachel have is their marriageability.
But Leah was not jealous in the way of silly girls in love songs, who die of longing. (1.2.62)
Leah might have been jealous of Rachel's beauty, but she never has the angsty teenager kind of jealousy. Leah means business, so her jealousy is usually rooted in something pretty personal.
"I wandered in and out of the tent, eaten up by jealousy … my envy waned and I was horrified by the pain I saw on Leah, the strong one, the invincible ox who was on the ground trembling and wide-eyed." (1.2.73)
Here we see how jealousy can trump Rachel's her love for her sister. Even when her sister could be nearing death, Rachel's still eaten up by jealousy.
Although she no longer hated Leah with the full force of the past, Rachel could not smile at her sister while her own body remained fruitless (1.2.110)
Jealousy isn't just a brief occurrence—it lasts a long time, much like a grudge. Again, though, this competition is deep rooted for these women, who can only survive in their society if they are good wives who can give their husbands children.
Bilhah barely breathed as the moments passed and her arms remained empty, but she said nothing. By law, this son belonged to Rachel. (1.3.20)
Now the jealousy shifts to Bilhah, who seems in most ways to be the least prideful sister. We can see here how much a child means to a mother—and how jealousy can erupt in even the most loving of sisters.
Rachel's old anger at Leah flared at that, but it vanished when she discovered that Joseph was a fretful baby who screamed and squirmed until he lay in his own mother's arms. (1.3.120)
As you can see, Rachel is a pretty jealous woman. Hmm, maybe the gods punished her jealousy by giving her years of miscarriages? The miscarriages, at any rate, certainly Rachel's problem even worse the more they happen.
She was no longer a child but a woman. I felt my cheeks grow warm with envy as hers grew pink with pride. (2.5.44)
Dinah feels the same way a lot of us do when going through puberty. It's almost like a race, and Dinah is losing to Tabea. And that's kind of bad, because it could mean that Tabea might snatch up the hot husband material first.
"For this is my son, Re-mose, child of Re, that you have born for me and my family." […] "Bar-Shalem," I whispered in his ear. (3.1.89)
Despite Dinah's promise to bear her son on Re-nefer's knees, she cannot help but try to make Re-mose her own. Her jealousy against Re-nefer doesn't subside, even though her chance of being kicked out of the house is a great to risk.