Angel in America
The Jinni develops an appreciation for this statue in Central Park because it's a supernatural creature—and she's human, but not quite, just like he is. Central Park is a place of peace to the Jinni; he loves being "stunned by the vivid sea of green" (7.41). He notes that "the artist had sculpted her with reverence, not fear" (7.46), and he later brings the Golem to see it. For the Golem, the statue represents the "calm, peaceful" (17.137) part of New York City that the Golem longs for.
Here we can see the angel as representing something generally unattainable but intensely desirable for both the Golem and the Jinni. In the absence of fear that the Jinni recognizes in her construction, there's the acceptance of a powerful supernatural creature that's missing from his life. And for the Golem, her struggle to make her way as a supernatural being in New York is far from peaceful—but she sees this peacefulness in the angel. The angel, then, sort of mirrors their desires.
The statue is a little more complicated as a symbol, though. Although the Jinni identifies with the statue's otherness, she's the angel of the waters, and water and jinni don't exactly mix. When he decides to destroy himself, he does so by drowning himself in the statue's bowl of water. In this act, we see him coming right up against his desires—he can't get what he wants and he's drowning (metaphorically) in this lack, so he goes to the angel and tries to put himself out of his misery.