This illusion only works if we accept that there is a lot of twist-away from us, the viewer. Her eyebrow tells us she's nearly turned away from us completely.
We are actually seeing the perspective of looking from behind her shoulder/head (proven by us being able to detect the far-away lens of her glasses), and from a higher vantage point than expected, but our brains are deluded into perceiving a false square-on profile. Also the glasses are riding
very low on her actual nose.
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Many adult human females have very small button noses, which of course amplifies the cognitive dissonance of the elbownose. If this had been an oblique photo of an older man, with more weatherbeaten skin paired with a darker or in-shadow elbow, it almost wouldn't have been a significant illusion