@ sky
Dhani did not get sick as it was her fast, and she did not eat the food laced with narcotics. Viplav went out to the dhaba to eat with his friend, and therefore he did not get sick either. However, Tulsi's motives were to make most of the ashram residents incapacitated, so that she could do her prep without detection. Yes, you are correct in that these things were not too clearly presented.