When riddhima was attacked she sprayed on the attackers eyes and ran to vansh
Vansh was already shown outside
So i guess attacker is new girl or kabir who took away the letter
But to confuse the audience cvs r playing games with our minds so they showed vansh talking on phone saying he will take care if it now
Attacker is someone else not vansh ....vansh would spray on riddhima eyes and then put medicines he would never strangle riddhima when she is still not well.
Cvs knows if they shiw him real villian there show will go down
So to keep audiences on edge they show such scenes of vansh