My [interpretation? fanfic?] is that Julia is like a carnivore, and humanity is not it's first prey. Every creature that eats, eats to steal the disentropy of it's meal. Plants can steal order from sunlight, and certain microbes can steal order from thermal vents, but carnivores, herbivores, and decomposers steal order from the work of other organisms. The improbability of living is sustained by arranging stolen amino acids into one's own proteins, powered by the toppleing of sugar towers back into a jumbled mess.
Julia does not reassemble amino acids like earth life does. But it does absorb disentropy from it's prey. The extreme specificity of an interstellar spacecraft, it's contents and occupants, is absorbed by Julia, so that it can move, grow, and attract more prey.