Number One - Paro was UNCONSCIOUS when the whole tragedy happened and Varun Sa's true face appeared. She only saw Rudra shoot him dead.
Number Two - Rudra did not leave anyone alive as a witness who can tell Paro or the BSD seniors the truth of that operation.
So, no matter how right Rudra and how wrong Paro is, the fact is that he cannot prove anything. And when you cannot prove anything, you have to either put a trap , create a situation or wait for a 'Lohaa Garam Hai' moment for the other party to SEE the truth on their own.
It was very frustrating today to see Rudra go to the extent of giving a pistol in Paro's hand to shoot herself , and how angry and helpless he felt as his desperate attempts to make Paro see the truth fell flat on Paro's "Sab jhooth hai" ears. He knows he is right and Paro is only endangering herself and going closer to jaws of death - and it showed in his panic and his frustration.He tried to put the reality picture in front of her with angry desperation , even told the truth of Varun, he told her to shoot herself dead because what she is doing by not believing him is as good as suicide. But Paro physically and mentally shoved him away - She only believes her eyes and her eyes, they have told her all lies.
Point being, this truth has no proof. And when truth has no proof, it waits for a LIVE demonstration and a cliffhanger crescendo where it can display itself in full glaring glory to the non-believer.
Perhaps that is what is going to happen with Paro. The only way she will believe Rudra is when she will go into jaws of death. And what Rudra told her before she shut the door on him is what the future is - he really sounded like a fortune teller:
"Fine, if you don't want to believe me , don't believe me. But one day when death will come and stand in front of you, and i will not be there to save your life, you will remember this whole convincing that am doing as a supercool flashback."
Paro had shuddered at the sight of the pistol when Rudra gave it in her hands. What will she feel when an assassin actually comes and holds her at gun-point? If nothing else, she will definitely remember all the desperate frustration Rudra showed today, in trying to convince her that he is the only one who wants to keep her alive.
Not that am blaming Paro. You can't. The problem here is the situation. And Paro's situation is such that she will have to FACE the truth to KNOW the truth.
Someday, she will know, in a very horrifying situation that her 'destroyer' was always the 'destroyer of evil' - Rudra.