The reason why Rashami doesn't want Arhaan going after Vikas is because Vikas knows how to walk away from an argument and look like the bigger person. Also he knows how to put forward what actually happened and make Rashami and Arhaan look like the culprits they are. Vikas figured out their game and called them out on it and Rashami doesn't want him to continue to call them out. Even Asim was upset and was asking BB to take Vikas to confession room and stop him from messing up their fun.