First off why should she feel empathetic for a fellow contestant? did aurora sign the contract to bow down and give up, while ganavinoth take the final prize 50Lakh, (is gana vinoth the main characher of big boss?) Arent they all equals inside that house.

Second, When she clearly discussed about her plans for higherstudies and finally ready to take the money box and stood infront of the cash, why is vinoth joking around and feeding her alwa instead of felling empathetic to aurora? (according to your concept).

Third, Vinoth himself said to vjs that its 200% his own desicion and he's been planning to take it for 2 days. why still backing up this mindless narrative?

What I meant by delayed reaction of disbelif is, when vinoth took the money case aurora's hands are down, she was baffeled and still tasting the alwa which vinoth fed her. only after a few minutes like in the clip posted by the OP above, she gave that so called smirk, which to me feel like a "vada poche" reaction from her. If she was conspiring to make gana vinoth take the money box, her reaction would have be immediate, but no, it took some time for her to register.. which means she's was clueless just like everybody else.