Concept:Use circular arrangement with anticlockwise as left and clockwise as right.
Explanation:Place Pappu at any position.
Subbu is to the left (anticlockwise) of Pappu.
So Subbu is one step anticlockwise from Pappu.
Aruna is between Pappu and Keerthna, so Aruna is clockwise from Pappu, and Keerthna is next clockwise from Aruna.
Now Subbu and Nisha have Revathi between them; the only empty spots adjacent to Subbu are anticlockwise from Subbu, so Revathi fills that, and Nisha fills the next anticlockwise spot.
The clockwise order (from Pappu) becomes: Pappu, Aruna, Keerthna, Nisha, Revathi, Subbu (and back to Pappu).
Nisha is at position 4; her right (clockwise) neighbor is Revathi.
Answer:Revathi (Ravathi)