Sometimes a person's spouse knows him better than he does. Einar is one of those people who is almost entirely unaware of himself. We're surprised he can even function without his wife.
"I'd do it for you." (1.15)
Greta is entirely devoted to her husband, and she would do anything for him, even when "him" wants to become a "her."
By spring of 1925 they had been married for more than six years: on certain mornings it felt to Greta like six weeks; on others, six well-lived lives. (2.1)
Neither of these seem like a bad thing to us, with the adjective of "well-lived" added before "lives." It seems like Greta feels like she is sometimes still in a honeymoon phase with Einar, and other times it feels like they've had such a good marriage, it can hardly be contained by one person.
It was a small wedding, only cousins from San Marino and Hancock Park and Newport Beach. (4.44)
Greta's family wants to keep it small because they are embarrassed. We're unsure how many people attended Greta and Einar's wedding later. What do you think their wedding looked like?
She could defy anyone in the world except her husband. (8.10)
Once again, we see Greta's devotion to Einar—and here it foreshadows the fact that she will defy Lili later on. Greta married Einar, not Lili. Lili isn't her husband, so Greta can defy her.
"Don't you think marriage is the one single thing we should all hope for most in life? Doesn't it make you more whole than living alone? […] I think it does. Marriage is like a third person," Lili said. (9.75, 9.77)
Or fourth person, if you count Einar, Greta, marriage, and Lili.
For a moment, Einar felt like defying his wife. (9.16)
Compare this with the previous quote. It doesn't seem like a huge difference, but it is. Greta wouldn't even think of defying Einar, and although Einar doesn't defy Greta, he thinks about it.
"This is a special wedding. I see something special here. In ten years the two of you will be extraordinary people." (11.19)
This is a brief flashback to Einar and Greta's wedding day. But it's not like anyone ever says, "These two boring people will still be boring married people forever," though, so as far as foreshadowing goes, it's pretty vague.
Part of Greta wanted to be married to the most scandalous man in the world. It had always annoyed her when people assumed that just because she had married she was now seeking a conventional life. (12.15)
Greta married Teddy partially because her parents would hate it. That's another reason she considers staying with Lili even though Lili is no longer her husband—they still live together like spouses because Greta likes to go against the norm.
Lili had always wanted this. She knew one day she would marry; sometimes, when she thought about it, she felt she could play no greater role in this world than as a man's wife, Henrik's wife. (27.4)
In contrast to Greta, Lili wants to adhere to traditional gender norms, which, in the early 1900s, means being a dutiful housewife. How do you feel about Lili giving up Einar's career as a painter to become a wife?