The two primary settings for The Great Gatsby by F. Scott Fitzgerald are East Egg and West Egg in New York. Each is distinctive not by sight (as the birds flying overhead are likely to be confused about which is which) but by the people who live there. Both East and West Egg are populated by the rich; however, each group got its money in a different way.
East Egg is where Daisy and Tom Buchanan live. It is the place where the people who have what is called "old money" live. Old money is inherited family money (think Rockefellers and Kennedys, for example), and the presumption is that these people are more genteel, moral, and refined than other people due to their privileged status. They have been raised with good manners, we assume, and their morals should therefore be of a higher standard.
In contrast, West Egg is where Jay Gatsby (and of course Nick) lives. The people here also have money (except for Nick), but they have earned their money through business or other unsavory means. This is called "new money." In the case of Gatsby, we know that there is a significant illegal element to his money based on many clues throughout the novel: his association with Meyer Wolfshiem, his mysterious business phone calls, his "in" with the political machine, and more.
The presumption is that since these people are new to their money, they are less cultured, less refined, less moral and thus less worthy of being rich than those with old money. This is exactly why East Eggers generally despise West Eggers.
The irony, of course, is that in this novel it is the East Eggers who demonstrate the worst characteristics. In fact, it is the East Eggers who flock to Gatsby's West Egg parties, and we know they act carelessly and without morals while they are there.
Your question asks about Daisy being appalled by East Egg; however, in chapter six Daisy says she is appalled by West Egg. Note the following:
She was appalled by West Egg, this unprecedented “place” that Broadway had begotten upon a Long Island fishing village — appalled by its raw vigor that chafed under the old euphemisms and by the too obtrusive fate that herded its inhabitants along a short-cut from nothing to nothing. She saw something awful in the very simplicity she failed to understand.
Again it is ironic to note that while Daisy does avoid Gatsby's West Egg parties, she loves Gatsby (or at least loves the idea of loving him). She also considers West Eggers to be less than herself, yet it is a West Egger who is fully prepared to take the blame for her action--running over Myrtle Wilson. Gatsby, a West Egger, is loyal when she is not. It is a West Egger (Gatsby) who is unwilling to accept a divided love (Daisy loving both Tom and Gatsby) while an East Egger (Daisy) is perfectly willing to let her husband have a string of lower-class mistresses, beginning as early as their honeymoon.
So, the things Daisy disdains about West Egg are the very things she does. Nick says she is a "careless" person, and she is. Her old money buys her many things, but it does not buy her morality, goodness, kindness, or true happiness.
For more insights and analysis on this classic novel, see the excellent eNotes sites linked below.