With enough time and age her envy of her friends' lives had diminished and become manageable; but still, even now, when the Christmas letter arrived Jules allowed herself to experience a new, small surge of a very old feeling. (3.1)
Notice that Jules "allowed herself" to feel jealousy, like it's a treat or something, a bit of ice cream when you're trying to eat healthily. For all of the ways that being so jealous seems to make Jules miserable, it also seems like she kind of enjoys it.
This concentrated and renewed burst of ancient Ash-and-Ethan envy had turned Jules into someone shameful. And it wasn't as if Ash and Ethan didn't have problems too. First of all, they had a son with an autism-spectrum disorder. (3.60)
This is really the only thing Jules ever brings up that's wrong with Ethan and Ash's family. Why is Mo the go-to symbol of them not being overly successful? It's not like having a child on the autism spectrum indicates failure for anyone involved, so we're thinking that Jules's association of this with failure doesn't reflect favorably on her.
But maybe Cathy Kiplinger was annoyed because she was jealous. Everyone wanted to be held by Ash, not even to evoke a sensual feeling but just to have been singled out. (5.6)
What on earth is so special about Ash that everyone wants to be singled out by her? Seriously—what do you think it is that compels people toward her?
I will never be in a profoundly messy situation with a boy, Jules Jacobson thought with an unaccountable little burst of despair. (7.166)
Jules is jealous of a girl who was probably just raped, because she wishes she could get that level of attention. We don't even know what to do with Jules anymore. Ugh.
Clearly she'd undervalued him, she thought now darkly, as she stood […] without a piece of silicon snapped deeply and securely inside her, […] waiting to be put to use. (9.26)
Jules only thinks she's "undervalued" Ethan because Ash is going out with him now—she's jealous of Ash and her relationship and her sex life. So much jealously despite repeatedly rejecting Ethan earlier when he expresses interest in her.
It was darkly fitting that Jules herself, who envied her friends so powerfully, would have an envious daughter. (13.120)
Rory may be envious, too, but she doesn't rival her mother one bit. Rory is a much-more self-possessed person, and as such, can't be as consumed with others as her mother is.
"She and Rob had the most beautiful house in the canyon. And a place in Provence. I mean, I was jealous of their life." (15.78)
Can jealousy be a fake thing, or something a person claims because it gives them status in some way? Just wondering.
Sometimes in the past she's wished that Ash and Ethan's bounty had simply been taken away from them, and then everything would have been even, everything would have been in balance. (15.89)
Jules thinks that if Ash and Ethan simply and suddenly lost everything, all would somehow be even between her and them. But things have never been even—not in terms of money, and not in terms of talent—since Jules first gained entry to the cool kid circle. And, importantly, they've never been even in terms of jealousy, either; that's always been all Jules.
"Oh, that in keeping this promise to my parents, I basically chose them over him. He says he's always felt that anyway." (20.101)
Jules doesn't have a monopoly on jealousy, and even Ethan succumbs to it a bit.
"Your friends: Mr. loser gold tooth, and his lying sister […], and Ethan the magnificent, all of whom you've always worshipped beyond anything or anyone else on earth." (20.150)
We know jealousy is usually talked about as a negative emotion, one that hurts people. But what about righteous jealousy? After all, the things Dennis is saying here aren't wrong—and so perhaps his jealousy is an accurate response to Jules's adoration of her friends.