When Nikki throws the spider on Paulo and the spider bites him on the neck, paralysis is imminent. Instead he talks to her for a minute or two being able to move his head, blink and all. Then Nikki gets bitten in the leg and in a minute she drops down in the "dead" state. A bite in the leg would take at least a few minutes for total paralysis. She also didn't drop down and talk like Paulo did.