You don't know that. Nobody does.
We don't know exactly how aging works and this theory needs to be tested as well. If we stop research because we just know something, we'll never get anywhere.
"Her teeth, including her baby teeth, are like those of an eight-year-old. The length of the telomeres, on the other hand, corresponds to her actual age."
http://en.wikipedia.org/wiki/Hayflick_limit
"The Hayflick limit was discovered by Leonard Hayflick in 1961,[1] at the Wistar Institute (Philadelphia), when Hayflick demonstrated that a population of normal human fetal cells in a cell culture divide between 40 and 60 times. It then enters a senescence phase (refuting the contention by Alexis Carrel that normal cells are immortal). Each mitosis shortens the telomeres on the DNA of the cell. Telomere shortening in humans eventually blocks cell division and correlates with aging. This mechanism appears to prevent genomic instability and the development of cancer."
So basically she's gonna die from cancer after the average number of years.
But if her telomeres are shortening, doesn't that mean her aging will eventually catch up to normal because her cells stop regenerating?
It means she is aging. She is not developing.
Someday you may get a replacement organ in time due to r&d stemming from this girl's DNA.