Rhike Cyid Dhathron used Vinel Amin. He lied to her. He seduced her for his own purposes. Now, he has been subsumed by power and evil. He is the Falcon, a nightmarish thing of feathers and talons, more monster than man.
And yet, when Vinel is captured by Shaanti Jhaa and offered the chance to confront the Falcon and attempt to reach the man within, she takes it. The shaanti thinks that his old friend will remember Vinel, and that his feelings for her will be volatile enough to bring him back to himself.
Vinel knows that the shaanti can't be trusted, and she knows that the Falcon is dangerous.
Going to him doesn't make sense. She can't justify her actions to her friend and bodyguard Pruvana Deol.
Even so, all the same, she has to do it.