That "8 year old girl" was strong enough to contain 3 tails inside like it is nothing, even after her instant death, the bijuu seal wasn't broken, there was not a rampage by 3 tails. It took years for 3 Tails to emerge and be found by Akatuski. She did not give away any information during a torture by 2 jounins although she was only a genin at the time. She was quite something compared to her age.