The Madwoman in the Attic: on Middlemarch

The Madwoman in the Attic by Sandra M. Gilbert and Susan Gubar .
In chapter 14 "George Eliot as the Angel of Destruction", they argue that Casaubon and Lydgate increasingly resemble each other.

"When Rosamond expresses her opinion about debts that will affect her life as much as his, Lydgate echoes Casaubon 'You must learn to take my judgment on questions you don't understand' (chap.58). Lydgate contemptuously calls Rosamond 'dear', as Casaubon does Dorothea when he is most annoyed with her presumption. The narrator expresses sympathy for Lydgate's need to bow under 'the yoke', but then goes on to explain that he does this 'like a creature who had talons' (chap.58). Lydgate begins to act and speak 'with that excited narrow consciousness which reminds one of an animal with fierce eyes and retractile claws' (chap.66). Like Casaubon, Lydgate will 'shrink into unconquerable reticence' (chap.63) out of personal pride when help is offered. And like Casaubon he experiences the discontent 'of wasted energy and a degrading preoccupation' (chap.64). Fallen into a 'swamp' of debt (chap.58), he feels his life as a mistake 'at work in him like a recognized chronic disease, mingling its uneasy importunities with every prospect, and enfeebling every thought' (chap.58).
Lydgate had dreamed of Rosamond as 'that perfect piece of womanhood who would reverence her husband's mind after the fashion of an accomplished mermaid, using her comb and looking-glass and singing her song for the relaxation of his adored wisdom alone' (chap.58)- a dream not appreciably different from Casaubon's. [...] Lydgate attacks Rosamond's attachment to their house, thinking 'in his bitterness, what can a woman care about so much as house and furniture' (chap.64), but she has been given nothing else to care about..."

Earlier I have noted that Lydgate's mistake is not only his choice of a wife, but also his attitude towards women (which seems to have escaped some readers), the same way I think there's no denying that Casaubon's a horrible person to be with and Dorothea is wrong in unthinkingly taking a plunge into that marriage, but she also has some crazy ideas about a future husband. Another sexist in Middlemarch is the scatter-brained, trivial and ridiculous Mr Brooke. Contrast Lydgate with Will Ladislaw, who doesn't hold such views of women. The good people of the book such as Caleb Garth and Farebrother don't think that way either.
However, I think Gilbert and Gubar go a bit too far in their assessment of Rosamond:

"Having no overt means of escape at her disposal and a husband who refuses to hear or take her advice, Rosamond enacts her opposition as silently as does Dorothea; she is 'particularly forcible by means of that mild persistence which, as we know, enables a white living substance to make its way in spite of opposing rock' (chap.36). Always able to frustrate him by stratagem, Rosamond becomes Lydgate's basil plant, 'flourishing wonderfully on a murdered man's brains' (Finale). She fulfills Gwendolen Harleth's vision of women and plants that must look pretty and be bored, which is 'the reason why some of them have got poisonous' (DD, chap.13). Rosamond has been imprisoned by her marriage [...] In spite of the narrator's condemnation of her narrow narcissism, then, it is clear that Rosamond enacts Dorothea's silent anger against a marriage of death, Mary Garth's resentment, Bertha Grant's plot, Gwendolen Grandcourt's secret longing, and Janet Dempster's desire, as well as Maggie Tulliver's 'volcanic upheavings' (MF, IV, chap.3)..."

A few pages later: 

"The meeting between Rosamond and Dorothea is therefore the climax of Middlemarch. Both women seem childish because both have been denied full maturity by their femininity. Each is pale from a night of crying, believing that she has 'buried a private joy'. Each is jealous of the other, yet self-forgetful..." 

Not only so, they regard Rosamond as "Eliot's most important study of female rebellion".
It's this way of thinking, this approach to literature that I earlier found reductive and distorting if not even distasteful. What kind of person is Rosamond? She is selfish and egocentric, prioritising her interests and feelings above everything else, ignoring her husband and his sense of dignity, thinking about nobody but herself. She is extravagant, frivolous and carefree, refusing to economise, and riding a horse even when pregnant. She values money, social status and physical appearance- she does love Lydgate, but certainly wouldn't marry him if not for his good relations, and wants him to be more like the captain; she dismisses Mary for being plain, and asks if Mrs Casaubon is beautiful. She's not ashamed of her own actions, only of bad reputation and disgrace. She never finds herself wrong, just wronged by others. Her mind is narrow, she doesn't read, doesn't have self-reflection, doesn't question her own behaviour, doesn't have sympathy for others, doesn't strive for knowledge or self-improvement, doesn't care about anything but fun. Of course women have little to do in this period, but it's mostly because there's nothing on Rosamond's mind that she suffers from ennui and can only get pleasure from music, riding, parties and Will's visits.
Let's consider what happens when Lydgate talks to her about financial problems. She doesn't see the fuss, doesn't care about her husband's struggle and doesn't ask how she can help- what bothers her is the loss of respectability. She refuses to live in a smaller house or to sell some of their belongings, and doesn't want to spend less. Gilbert and Gubar say Lydgate "refuses to hear or take her advice", what kind of advice does Rosamond give? Ask for help. Keep the house and everything else. Take things lightly, lots of people have debt and still have respectability. Then she acts on her own, hinders her husband's efforts, and humiliates him before others.
Yes, Rosamond tells Lydgate of her disappointment. Yes, she says that when marrying him she didn't expect such difficulties to occur. But that's Rosamond's way of silencing and mastering Lydgate.
What I want to say is that, Lydgate and Rosamond are 2 individuals, 2 complex, multi-faceted beings. That Lydgate has a patriarchal view of women doesn't mean that he's an oppressor and his wife's a poor victim. It is simplistic to draw such a line, or to group Lydgate and Casaubon together simply because they're men (with the 19th century view on women) and group Dorothea and Rosamond together simply because they're women and unhappy wives. Their reasons for unhappiness are not the same- in Dorothea, mixed with disillusionment is pity for Casaubon; in Rosamond, there's an exaggeration of her suffering. Their ways of dealing with unhappiness are also different- Dorothea endures it and does what she has to do; Rosamond goes around doing things secretly and ruining everything for her husband. The only similarity is that they both find consolation in Will, but Dorothea is consoled by conversation and Rosamond, by music, which is more like a diversion.
I know, I know, a feminist critic might argue that Rosamond's narrow-minded and self-centred because of society and the limited possibilities for women, and so on and so forth. Please ask yourself if you haven't met several Rosamond Vincys in your life. 
And some people wonder why I abhor feminist criticism.