Lena’s marriage is best symbolized by...a balance sheet. (How romantic, right?)
She and her husband owe each other money, keep track of what they spend, and "split everything down the middle." It’s ostensibly to keep their marriage pure, but it’s obviously infected it instead. It’s also obvious that Lena is getting the raw deal, and worse, that she knows she’s getting the raw deal. But she’s too passive to do anything about it.
It might be that Lena is passive in her awful marriage because she feels like she’s getting what she deserves, karmic payback. If you recall, Lena was worried that she would have to marry awful Arnold, and wished him dead when she was eight-years-old. Since Arnold actually did die, Lena seems to feel that she’s getting what she deserved by being married to Harold.
Another take on their relationship is through the lens of communication. Growing up, Lena was often played the role of interpreter for her parents because her mom spoke little English and her father didn’t speak Chinese. But because the things Lena’s mother would say might be harmful to Lena’s dad, Lena would purposefully mistranslate to preserve the peace—even when it came to something as serious as her mother's mental health:
I could not tell my father what she had said. He was so sad already with this empty crib in his mind. How could I tell him she was crazy?
So this is what I translated for him: "She says we must all think very hard about having another baby. She says she hopes this baby is very happy on the other side. And she thinks we should leave now and go have dinner." (II.2.76)
Lena and her husband seem to have the same communication problem...even though they speak the same language. In an interesting reversal, Lena's mother has to translate for Lena when it comes to dealing with Harold:
"Lena cannot eat ice cream," says my mother.
"So it seems. She’s always on a diet."
"No, she never eat it. She doesn’t like."
"And now Harold smiles and looks at me puzzled, expecting me to translate what my mother has said.
"It’s true," I say evenly. "I’ve hated ice cream almost all my life."
Harold looks at me, as if I too, were speaking Chinese and he could not understand. (III.1.90)
And the reversal of mother-daughter roles isn't limited to translation. Lena tries to protect her mother when she's a child (which is already a little topsy-turvy in terms of normal roles) and Ying-ying tries to protect Lena when Lena's an adult.
Even though Lena tries to hide her marriage problems from her mother, Ying-ying sees that her daughter is making similar mistakes in terms of passivity and self-abandonment. Lena’s marriage is in many ways a recreation of her parents’ marriage, with Lena mimicking the way her mother acted as a wife.
Lena’s father, St. Clair, was in charge of her parents’ relationship, making all of the important decisions, including the decision to bring Ying-ying to America, to change her name to Betty, and even selecting the apartment they lived in. Ying-ying yielded to her husband because of the language barrier, but also because she wasn’t so interested in living – she called herself a ghost, and become more and more ghostlike as the marriage progressed.
Lena also yields to her husband, but with different justification: money. Lena makes less money than her husband, so he owns a larger percentage of their house, pays for the vacations, etc. He takes this a justification for making all of the home decorating decisions, deciding where their vacations will be, and so on. Because her marriage mimics her parents', Lena's becoming a ghost just like her mother.
Lena’s story ends with her mother attempting to show Lena the danger that she is in. Whether Lena will learn from her mother’s mistakes is unclear. Lena can see disaster coming in her marriage, but will she do anything to prevent it?