I dont get this.....

It was shown that Sarla chachi, gave Sandhya a glass of juice which had the tablets and she drank it, then how come there was no reaction on sandhya, but when sarla chachi had it, she started speaking out the truth and dancing and all...ow is this possible??

It seemed that Sarla had put the wrong tablets in Sandhya's drink the first time, and was trying a 2nd attempt, when Sandhya called her to sing, while she slipped out, found those tablets, slipped it into her drink & gave it to her. I found that plot rather ridiculous - someone like Sarla who's been outwitted by Sandhya already & has seen a genius like DK get his clocks cleaned would have been more wary of making such boo-boos

P.S. Last night it was revealed that Sunita, who spotted Sarla, spilt her driink and substituted it w/ plain OJ. Later, Sandhya put the tablets in one of Sarla's drinks. That reveals why nothing happened the first time. Nosy Sunita!