Originally Posted by Lead Cenobite
The way I took it is up until then, she had never realized that she didn't need to breathe, and it was only upon running out of air that she realized she could survive without it. In other words, her reaction, blacking out was all psychosomatic, sort of like Ursa in Superman II reacting to being bitten by that snake even though she was impervious to its bite.
Hmmmm, I guess that makes a lot of sense. Great way of looking at it