[Renegade334]

Well...

Spoiler:

In the Nightmare of Nunnally manga, she does open her eyes a scant second before her brother apparently gets crushed by a falling chunk of rock (his status is still unknown right now although there is a bionic Zero walking around O_O)...so we can assume that shock or extreme stress can, in certain instances, overcome her trauma and psychological block.

Not that it means anything for the anime, though... -_o