The Objectivist ethics does not look favorably on jealousy. The judgments that a jealous person makes of a rival are far from being models of epistemic objectivity, and jealous feelings are regarded as a sure sign of low self-esteem. In Ayn Rand’s fiction—most memorably, in Part II, Chapter IX of Atlas Shrugged—jealousy openly expressed is not just a badge of weakness but a near-guarantee of loss or rejection.
In the context of Rand's theory of emotions, jealousy must be regarded as a product of value premises, rather than an innate predisposition triggered by specific circumstances. Did Rand present any evidence that jealousy was an acquired rather than an innate predisposition? No, of course not. Does such evidence that exists on the question tend to support Rand's view? No, it does not.
Jealousy is very commonly observed, widespread emotion. It exists in all cultures and affects nearly everyone (though some people may be more prone to it than others). Experiments show that it can easily be triggered, even people who don't regard themselves as the "jealous type."
David Desteno and Piercarlo Valdesolo decided to test how easily jealousy can be triggered in individuals:
We orchestrated a complex social reaction that stimulated ... how jealousy naturally occurs in the real world: a relationship starts, it's threatened by a rival, and then it actually dissolves due to the rival.... Basically, the unknowing participant was being set up for the ultimate brush-off. Why would we put people through this? Because, harsh as it might sound, it is the most valid method of studying how jealousy works in everyday social interactions. [Out of Character, 85]
The initial experiment worked as follows. Carlo Valdesolo pretended to a be a participant in a psychological experiment which involved answering trivial questions. He pairs up with a female participant and immediately begins flirting with her. A little later, another female enters the room, allegedly to take part in the experiment. Carlo begins flirting with the new female "rival," until he suggests to her, "Why don't we pair up," leaving the other female participant, the true subject of the experiment, to stew in her own juices.