The Great Gatsby- Myrtle Wilson's Pitiably False Sense of Wealth

Mrs. Wilson had changed her costume some time before and was now attired in an elaborate afternoon dress of cream colored chiffon which gave out a continual rustle as she swept about the room.  It's interesting to note that it's supposedly evening by now. Someone of true social status, acutely aware of fashion, like Daisy, for example, would never have picked an afternoon tea dress for an evening get together with friends. This shows Mrs. Wilson's social naiveness and also the shallowness of her ability to be a "rich person."
With the influence of the dress her personality had also undergone a change. The intense vitality that had been so remarkable in the garage was converted into impressive hauteur. Her laughter, her gestures, her assertions became more violently affected moment by moment.....  It is interesting to note here that Myrtle is two different people. At the garage with her husband, she is ordinary, plain, boring, and essentially middle-class. With Tom, however, she becomes a new person, flirtatious and beautiful and on the surface, wealthy.
She told her sister in a high mincing shout, "Most of these fellas will cheat you every time. All they think of is money. I had a woman up here last week to look at my feet and when she gave me the bill you'd of thought she had my appendicitus out." The lack of proper pronunciation (saying "fellas" instead of "fellows" or "gentlemen", mispronouncing appendix) definitely would indicate to someone of Fitzgerald's era a large sign that Myrtle is really not wealthy- most wealthy people in the early 20th century talked educatedly. Also, someone like Daisy would never mention the cost of medical bills- the Buchanans don't care about who or how they spend their money- they're too rich to mind.
...... "I like your dress," remarked Mrs. McKee. "I think it's adorable." Mrs. Wilson rejected the compliment by raising her eyebrows in disdain. "It's just a crazy old thing," she said. "I just slip it on sometimes when I don't care what I look like." This section, actually, is quite hilarious. The reality is, Myrtle most likely begged for the money from Tom and went out and carefully bought it. The fact that she is trying to overtly sound like one of the upper class is humorous.
...... She turned to Mrs. McKee and the room rang full of her artificial laughter. "My dear," she cried, "I'm going to give you this dress as soon as I'm through with it. I've got to get another one tomorrow. I'm going to make a list of all the things I've got to get. A massage and a wave and a collar for the dog and one of those cute little ash trays where you touch a spring, and a wreath with a black silk bow for mother's grave that'll last all summer. I got to write down a list so I won't forget all the things I got to do." 
Again, here Myrtle is overtly trying to sound like an upperclass lady. Then- the list making. Don't all rich people make lists? In reality, Daisy would have probably hired someone to make the list and then shop for it. Oh, Myrtle... you have so much to learn.