In other words, I believe my Ni dominance was hidden: that it is what made the whole video appear to be easy, effortless and spontaneous.
Interestingly, (MBTI-knowledgeable) people have watched videos of my salsa dancing and said, "It is sooo obvious you are an INTJ when you dance." Why? An Se dom moves his whole body, everything is moving with the music, following beats that you wouldn't even hear except his body movements point them out to you. I don't do that: my movements tend to stay very smooth and controlled, and my gaze stares off into space. As one ESFP dance teacher told me, "HEY! Look at me! Look at your partner." I have to make a conscious effort to do that.
Also, I suspect that we tend to latch on to one of the two axes more quickly than the other, and try to make the other fit. Most people would start off typing her as NF (due to her music and personality), spot the obvious Ne, and then say INFP, or instead see her as more introspective and lean toward INFJ. The visual typing instead starts off spotting the very obvious Ne, plus the introversion, and is thus stuck choosing between INFP and INTP, and her smile is more typical of Fe. (Again, I think it's more that may very well be genetic, and not an unconscious expression of Fe.)
That would indicate two potential flaws of the visual typing system. 1) people temporarily expressing their inferior side, and 2) people with facial expressions that genetically resemble the cues for a type in most other people, but not the case in hand.