I have a feeling that she's not immune to age, but growth. When she hits 30 I think they're going to start noticing signs of age like wrinkles and stuff, so she'll be like one of those kids who suffer from old age even though they're only children. It's a pretty remarkable story, but it's sad. Never growing old is the fantasy of many people, but that's quite different from simply never growing. I'm sure she's perfectly happy simply because she can't comprehend the strangeness of her existence, but it's still sad that she'll have to go her whole life not experiencing anything more than that.