Jealousy, that mischievous green-eyed beast, plays a central role in "Bernice Bobs Her Hair." Even though its antagonist, a girl who seems to have it all, realizes full well that she, um, has it all, she still can't help but be jealous. In "Bernice Bobs Her Hair," jealousy is simply a fact of life, especially when the person in question is a popularity-obsessed teenager who's used to getting everything she wants. Fitzgerald reminds us of the bitter truth – even when we don't realize it, we're often jealous of someone. It sneaks up on us unawares, and sometimes we don't even recognize it until its too late. Once released, though, jealousy is almost impossible to rein in.
Marjorie's jealousy of Bernice stems from the fact that Bernice ultimately becomes more successful at being Marjorie than Marjorie is.
Warren is the only motivating factor in Marjorie's jealousy of Bernice and her ultimate betrayal; this demonstrates the inevitably destructive intrusion of male influence in a friendship between women.