It really did happen that fast. From Gio's perspective, it was a lot easier to see everything as it was since he didn't have to think about anything else.
He'd been watching Natalia and Mother Baba aim for each other's necks, so he was able to somewhat glimpse the events that led up to the worm's appearance.
In fact, if he had to guess, Mother Baba had first called it some time ago. She may have even called it when she first used her vitality.
However, the worm took a long time to arrive. When she finally sensed its presence nearby, her switch flipped. She went crazy, laughing so loudly that even Gio, who was far away, had to cover his ears to avoid being hurt by the screeching.
Her words cut through the air as she mocked Natalia, and then, as it happened, the sandworm showed itself.
