i think it is neti who killed antra directly or she arranged some1 to kill her.remember she was speaking on phone with some1 saying sub kuch ghalat ho gya. maybe she killed her.
i predict becoz we r forgetting neti came for a revenge and everything is happening after wards. it is all her plan.
i think neti got antra killed and wrote D with antra's blood on the handkerchief so that druv gets framed.coz if druv gets framed kk will cry and she wants to take revenge with kk by giving her pain. she know that police knows that druv called siya to talk in terrace, so she knew by framing druv, siya wud also be framed and police wud think that it is their plan to kill antra thats y druv called siya, so that antra can get out of their way.
i think master mind behind all this is neti.thats wat i think,LET C.