You may both be right, Jim and Dick.
An individual singer with plenty of intuitive musicality, and experience of singing and listening, may use ornamentation in the most appropriate and expressive way, without stopping to think about it.

However, most singers lack some of those advantages, and may benefit from stopping to think about what the ornamentation is for: e.g. in unaccompanied singing, it can serve to put the melody into a harmonic context; it can also add expression to a particular word, etc etc. It should always have a point, even if the point is simply decoration.

In that broadcast, it sounded to me as if Rachel had decided where and how the ornamentation could best be used, and had then got it "wrong" by her own high standards. All credit to her for making the effort and wanting to make the song as good as it could possibly be. Many singers could learn from her (I'm sure I could!). I hope she does well.

Marje