Okay, you were concerned about flames, considering Gabrielle's age. She's more than half-Veela. They mature must faster than humans. The only human trait it appears she has is that she's flat-chested.
Veela mature quickly and live long lives from what I understand. At eight years old, Gabrielle is just coming into her prime. It's just that Harry's seeing the human part of her and thinking like a human. A human 8-year-old girl wouldn't have presented herself that way either.
No flames here, but it does cry to continue. Good job.