When the novel starts, Nick visits his cousin Daisy and her husband Tom in their mansion. They have another guest, Jordan Baker, a well-known tennis player. When Nick first meets her, he does not know who she is, and so sees her as someone aloof from the proceedings:
If she saw me out of the corner of her eyes she gave no hint of it -- indeed, I was almost surprised into murmuring an apology for having disturbed her by coming in.
(Fitzgerald, The Great Gatsby, mrbye.com)
His first reaction is that she is arrogant, but justified in her views because of her status. He can see at once that she comes from a higher social position than he does, and so her interest in him comes as a surprise. However, Nick tries to be a good companion, seeing her partially as an entrance into the upper-class society of the Easy Egg that he might not be able to attain otherwise.
"with her chin raised a little, as if she were balancing something on it which was quite likely to fall"
"the object she was balancing had obviously tottered a little and given her something of a fright"
These quotes demonstrate Nick's reaction to different social classes. Nick is the one narrating and everything we hear in the novel is baed upon his own judgement and perception.
And for context, this reflects Fitzgeralds views on social classes.