i agree with bella, thats. quite a good point. it could be from the low gravity area since she was exposed in her earlier years as a child then suddenly brought back to earth. I think her body is trying to regulate with the earth’s atmosphere but ofcourse shes still a kid and her body is very fragile as a child
They are in earth, yes? But we can see they’re inside a ship (?) and its conditions are somewhat different from Earth I believe to accommodate the aliens. Because remember in the prev chapter, Lily’s dad would kind of melt due to the difference in gravitational forces. And we dont see that inside their ship so its conditions are indeed different from Earth, explaining Lily’s condition.

Is this why she collapses because her early development was in a low gravity area ? Or because she was in water for a while as an infant or something else ?