Police found Rs. 20 lakhs in her possession.
She had said a few days before the attack Zahran had given her the money.
Earlier she had criticized Zahran and his actions.
Speaking to the BBC Sinhala Service, she had said: "I knew about his activities from media, and I never thought that he would do such a thing. I cannot think what will happen next... I totally oppose what he has done, and he is my brother, but I cannot accept this. I will not think of him later on. "
A few days earlier, Gafoor, Zahran's driver, was also taken into police custody.
Madaniya had commented to the BBC: