In this image here, shared by Kristine to the Daily Mail, you can clearly see two adult central incisors. The teeth either side (the lateral incisors) should be similarly square and flat, almost but not quite the same size. These are considerably smaller and more peg like. This would put N at 7-8 years old.
Baby Teeth Eruption Charts - American Dental Association
Once again, the only source for her having a *full* set of adult teeth (as opposed to the rather woolly statement of "her dentition was described as adult" in the doctor's letter) is Kristine.
N was an legal adult at that point because the Barnetts had changed her birth certificate. The CPS won't become involved with a legal adult. N was very, very lucky indeed to have been taken in by the Mans and not someone more sinister.
I suspect the charge of abandonment was made because it side steps the sticky mess of her age entirely.
Once again - legally she's an adult. Even if she is reverted back to her original birthday, at this point in time she is legally an adult, and they can publish her pictures with no concern.