"Yes miss, you are," she cried, and her words were all broken. "Whats'ever 'happens to you—whats'ever—you'd be a princess all the time—an' nothing couldn't make you nothin' different." (7.206)
Even though Sara is penniless, Becky still considers her a "miss." So, is class something that's innate? Or can it be gained and lost, like money?
When she went down to breakfast she saw that her seat at Miss Minchin's side was occupied by Lavinia, and Miss Minchin spoke to her coldly. (8.7)
Uh-oh. As soon as Sara is poor, Miss Minchin moves her away from all the other girls. How rude!
"To think that she was the girl with the diamond mines," Lavinia commented. "She looks like an object." (8.17)
Thanks for the observation, Lavinia. That's a very nice thing to say about someone whose recently been orphaned.
And afterward she was called by all of them, "The-little-girl-who-is-not-a-beggar," which was, of course, rather a long name… (10.24)
Even though she looks like a beggar, dresses like a beggar, and is hungry like a beggar… Sara's still got the manners of a real lady, and it shows.
Her face went red and then it went pale, and for a second she felt as if she could not take the dear little sixpence. (10.8)
Sara is super embarrassed to be mistaken for a beggar, but she doesn't want to hurt little Guy Lawrence's feelings—so she takes the sixpence. That girl is a class act.
And so when the servants, taking their tone from their mistress, were insolent and ordered her about, she would hold her head erect and reply to them with a quaint civility which often made them stare at her. (11.25)
Sara's a true lady even when taking orders from the cook. We wish our servants were so polite. (We kid! We kid!)
"If I'm a princess," she was saying, "if I'm a princess--when they were poor and driven from their thrones—they always shared—with the populace—if they met one poorer and hungrier than themselves." (13.33)
When she's hungry and can't take it anymore, Sara still offers to help out the poor child in the street, 'cause that's the high-class thing to do. Obviously.
"So I see," said Miss Minchin witheringly. "With Princess Sara at the head of the table." (15.206)
Miss Minchin has some sense of humor, huh? Oh, wait. We're not laughing.
"… Ermengarde had taken up her hamper to share with Sara and Becky. She never invites us to share things. Not that I care, but it's rather vulgar of her to share with servant girls in attics." (16.14)
Lavinia really cares way too much about who you should and should not associate with, and not nearly enough about how you treat people. Come on, Lavinia. Aren't you nearly a grown up?
"There are not many princesses, Miss Minchin, who are richer than your little charity pupil, Sara Crewe, will be." (18.55)
Of course, at the end, the joke's on Miss Minchin and Lavinia because Sara now has all the class and the money in the world. Take that!