And from spectrogram, it's the strongest signal (it went from B6 [1975.53 Hz] to E6 [1318.51 Hz] at the end when she was letting the note go):
I am no musician, so this is "only" engineering perspective.
Based on vocal ranges website I found, there is not many people who can go up to B6.
And this was done with Dara's main voice vocal range (when young - around or under 15 years old), not whistle notes done by special techniques (and holding the note for almost one good second). Once again, I am no musician :). I was just curious. I am not even sure if that's the highest note on Dara Rolins' recordings. I just felt like it's pretty damn high. Music is made to be appreciated, not for hitting the highest notes (but in this particular case the note and the way it was sung is stunning). Flavor and technique of the tones is important as well.
And I verified the tone with piano recording spectrogram (to make sure I am doing the spectrogram right):
I used Python and following libraries: