Bernice's statement to Charley about wanting to be a “social vampire” at the bridge party isn’t necessarily what it seems. Through this quip, Fitzgerald explores the contrast between Bernice's declarations and her real intentions:
"I want to be a society vampire, you see," she announced coolly, and went on to inform him that bobbed hair was the necessary prelude.
Bernice's declaration here does two things: it makes her seem daring, and it gives her the same aura of defiance that the bob she’s talking about getting would convey. This decision to adopt a new, provocative persona contrasts with her actual intentions, as she has no real inclination to cut her hair whatsoever. The situational irony here centers around the fact that talking about the bob makes Bernice seem attractive, while getting the bob is likely to do the opposite. She’s saying she wants to get a bob because it’s interesting. However, while it makes her more intriguing to her peers, the actual act of bobbing her hair would very likely lead to social disapproval.
The people at the party are more engaged by the idea of Bernice with a bob than they are with her normal shy personality. They find the concept entertaining, and it makes them look at her in a new light. It’s safe, for them as well as Bernice, as long as it remains hypothetical. The situational irony here points to a gap between social conversation and acceptable behavior. Bernice uses the image of bobbed hair to gain attention, but she stops short of actually making a definitive change. Discussing radical ideas, as Bernice learns here, can be more socially beneficial than actually taking action. It's all well and good until Marjorie and Otis demand she makes good on her boasts.
One might expect Marjorie to show jealousy or anger when she hears that Bernice has captured Warren’s attention, as he was previously only interested in her. However, in a situationally ironic gesture, she laughs and claims she is pleased that Warren has found someone who appreciates him:
Marjorie on being twitted only laughed. She said she was mighty glad that Warren had at last found some one who appreciated him.
This response is ironic because it's the opposite of how a reader might expect Marjorie to act when faced with an event like this. Having been embarrassed by Bernice previously, Marjorie would plausibly feel angry and shocked that her awkward cousin had displaced her. However, Marjorie's laugh and remark suggest she's totally indifferent to Warren's preferences. It hides any potential feelings of jealousy or annoyance she might have. Moreover, her comment actually devalues Warren's desirability, which also minimizes the impact of Bernice's social success. Marjorie appears in control and unaffected, preserving her social standing at a moment where it briefly looked tenuous.
Additionally, by reframing Bernice’s success as a criticism of Warren, Marjorie deflects any suggestion of personal inadequacy that the situation might otherwise provoke. Her poised reaction is clever and manipulative. It shows Marjorie's adeptness in maintaining her position in her social circle. It also shows that she’s not above being cruel about either Warren or Bernice in public.
