As the girl who kidnapped Irina was fighting with Astron and keeping her life on the line, naturally, she wasn't able to keep the restrictions that sealed Irina's mana.
And because of that, even while Irina was unconscious, her body gradually recovered the mana it lacked. After all, before everything, Irina was a member of the Emberheart Household, and she was a prominent mage.
Her body had the innate abilities that were related to mana. Starting from mana recovery to mana integration, everything was engraved in her genes to some point.
Therefore, she easily recovered from the state of mana exhaustion, and her body returned to its supernatural nature.
And because of her fast recovery speed, Irina was able to wake up from her unconscious state thanks to the loud voices of things exploding and clashing.
After all, even though she was yet to be completely aware, she was in the fighting stage.