Sana's character is negative from day 1. She had 2 days worth of "feel sorry for me I am an in-adept orphan" but after that she has been anything but positive. Naina decided to go after a married man based on conversations she had overheard...Is that the sign of a character being positive??? Naina knew that Sid was in pain after breaking up with Roli but she did not care. She was in love with Sid and she wanted him; she did not really care that the feelings have to be mutual...another point that she is negative.
It was confirmed that Naina is negative the day she slept with a married man and instead of regretting her decision and repenting she was abusing and bashing Roli. Sid kept telling Naina I dont love you and what happened between us is a mistake and the fact that she does not believe him proves that she is psycho
Do you need any more proof about Naina being negative?? The fact that she accepted a character where she has to play the "other woman" itself proves that Sana knew what she is signing up for