@17:34 she puts the blindfold on, pulls it down over her nose into what would logically be the most comfortable and sensible spot (where the bridge of the nose meets the gap created for it in the blindfold design),
but she then immediately adjusts it,
pushing it back up into a spot which makes no sense. Its obvious to me that the only reason to do this is to enable the ability to peek. (I love the "convincer" she does of initially putting the blindfold on upside down, because she can't see it, right?) She's absolutely letting the mask ride too high up her face, and she keeps tilting her head back at exactly the moments I'd be doing so to peek. I love illusions, but only when the audience knows what they're paying for!! When its presented as real, its painful to watch.
@18:46, at the precise moment she'd need to peek at the colour of the pen being chosen by the spectator, she tilts her head back (to better enable the peek). After the card has been written on, her helper moves it past & behind her, at which time she turns her head hard right (to better enable the peek). Its almost like she knows exactly where he's moving the card! He then shows her the card directly, holding it relatively low, in the perfect spot for her to peek without tilting her head back. He then goes to take her hand and she immediately holds her hand out and looks downward directly at his hand. I could go on...
A problem with the "third eye" logic: Notably, if we grant that she has to look towards things for her
third eye to see them, its obviously a given that her third eye can see THROUGH the blindfold. So why can't her third eye also see, for example, through the back of a card that's been written on? Or through an envelope its been placed in? No. Apparently her third eye can see through the blindfold & only the blindfold, but unfortunately, not anything else. She still has to have the card with the writing on shown directly to her for her third eye to be able to read it.

Perhaps third eye logic just doesn't work in logical ways. Its hard to tell, since mine clearly doesn't work at all.