Liiza's ice was far from superficial. It didn't merely affect matter. It stretched into ethereal, profound fields, making her able to touch intangible states of existence.
The Nak embodied the mana and were born and made of it. However, each member of that species wielded an individuality, a singular existence that Liiza could freeze.
Therefore, despite the more solid Nak losing its organs, tissues, and the very mana that made it, its existence continued to live, frozen in that ethereal, white status that only seemed to replicate what it once was, leaving it as a mere afterimage of its past self.
However, that enforced stillness wasn't absolute. The Nak couldn't move at all, but some of its functions remained active. Liiza had left its awareness intact to force it to experience that imprisonment for the entirety of its duration.