The implicit confidence that her destiny must be one of luxurious ease, where any trouble that occurred would be well clad and provided for, had been stronger in her own mind than in her mamma's, being fed there by her youthful blood and that sense of superior claims which made a large art of her consciousness. It was almost as difficult for her to believe suddenly that her position had become one of poverty and humiliating dependence, as it would have been to get into the strong current of her blooming life the chill sense that her death would really come. (2.2)
Gwendolen's expectations for herself are largely class-based. She can't imagine anything for herself but a life of luxury and good society.
[Gwendolen] had no notion how her maternal grandfather got the fortune inherited by his two daughters; but he had been a West Indian—which seemed to exclude further question; and she knew that her father's family was so high as to take no notice of her mamma, who nevertheless preserved with much pride the miniature of a Lady Molly in that connection. (3.4)
When the narrator says that Gwendolen's grandfather had been a West Indian, it means that he had made his fortune by going out to the West Indies and owning plantations. It seems as though this sort of enterprise – which could bring in a lot of cash, for sure – was not necessarily favored by "old money" types like Gwendolen's father's family.
Of course marriage was social promotion; she could not look forward to a single life; but promotions have sometimes to be taken with bitter herbs—a peerage will not quite do instead of leadership to the man who meant to lead; and this delicate-limbed sylph of twenty meant to lead. (4.2)
Gwendolen doesn't exactly want to get married, but marriage can provide a way to climb the social ladder. Gwendolen has many ambitions to get ahead, so it seems like she'll have to suck it up and get married.
The news was that Diplow Hall, Sir Hugo Mallinger's place […] was being prepared for a tenant, and was for the rest of the summer and through the hunting season to be inhabited in a fitting style both as to house and stable. But not by Sir Hugo himself: by his nephew Mr. Mallinger Grandcourt, who was presumptive heir to the baronetcy, his uncle's marriage having produced nothing but girls. Nor was this the only contingency with which fortune flattered young Grandcourt, as he was pleasantly called; for while the chance of the baronetcy came through his father, his mother had given a baronial streak to his blood, so that if certain intervening persons slightly painted in the middle distance died, he would become a baron and peer of this realm. (9.2)
This passage gives us a pretty telling glimpse into the way society works in Daniel Deronda. Grandcourt, who is sort of a total stranger to everyone so far, can just swoop in and wait for Sir Hugo to die because he's technically next in line for his estate. It doesn't matter how many kids Sir Hugo has if they're all daughters; they can't inherit his wealth.
"Mr. Fraser, how was it that the popes and cardinals always had so many nephews?"
The tutor, an able young Scotchman who acted as Sir Hugo Mallinger's secretary, roused rather unwillingly from his political economy, answered with the clear-cut, emphatic chant which makes a truth doubly telling in Scotch utterance—
"Their own children were called nephews."
"Why?" said Deronda.
"It was just for the propriety of the thing; because, as you know very well, priests don't marry, and the children were illegitimate." (16.2-6)
When society (or the church) frowns on something, just call it something else! Problem solved.
He had often stayed in London with Sir Hugo, who to indulge the boy's ear had carried him to the opera to hear the great tenors, so that the image of a singer taking the house by storm was very vivid to him; but now, spite of his musical gift, he set himself bitterly against the notion of being dressed up to sing before all those fine people who would not care about him except as a wonderful toy. That Sir Hugo should have thought of him in that position for a moment, seemed to Daniel an unmistakable proof that there was something about his birth which threw him out from the class of gentlemen to which the baronet belonged. (16.19)
Social class comes into play as a concern when Daniel wonders whether or not Sir Hugo might be his dad. When Sir Hugo suggests that Daniel might like to be a singer, he's horrified – singers belong to an entirely different social class than Sir Hugo does!
"Am I to go to school?"
"Yes, I mean you to go to Eton. I wish you to have the education of an English gentleman; and for that it is necessary that you should go to a public school in preparation for the university: Cambridge I mean you to go to; it was my own university."
Daniel's colour came and went.
"What do you say, sirrah?" said Sir Hugo, smiling.
"I should like to be a gentleman," said Daniel, with firm distinctness, "and go to school, if that is what a gentleman's son must do." (16.28-32)
Here we see class and identity mingled together. A younger Daniel aspires to be like a "gentleman" because in doing so he thinks he can somehow increase the likeness between himself and Sir Hugo.
"I am glad he is of high rank," said Mirah, with her usual quietness.
"Now, why are you glad of that?" said Amy, rather suspicious of this sentiment, and on the watch for Jewish peculiarities which had not appeared.
"Because I have always disliked men of high rank before." (20.43-45)
The rich don't just look down upon the poor – that relationship can go both ways.
"But I won't resign myself to live at Sawyer's Cottage and see you working for sixpences and shillings because of that. I shall not do it. I shall do what is more befitting our rank and education." (21.35)
Even though Gwendolen's family has lost everything, they still belong to the upper class as far as Gwendolen is concerned. Gwendolen sees marrying Grandcourt as a more appropriate remedy to their current financial situation than – heaven forbid – going to work.
"Besides, it has long been understood that the proprieties of literature are not those of practical life. Mrs. Arrowpoint naturally wished for the best of everything. She not only liked to feel herself at a higher level of literary sentiment than the ladies with whom she associated; she wished not to be below them in any point of social consideration. While Klesmer was seen in the light of a patronized musician, his peculiarities were picturesque and acceptable; but to see him by a sudden flash in the light of her son-in-law gave her a burning sense of what the world would say. And the poor lady had been used to represent her Catherine as a model of excellence." (22.51)
In Mrs. Arrowpoint's eyes, society is made up of categories of people who are allowed to interact in very specific but limited ways. Klesmer is cool with her as a musician and music teacher, but he is totally unacceptable as a potential son-in-law.