Hey guys Our Pallu is evil in Kasame Se, so evil that she killed two cutie children.
Anyways it can be guessed that she was evil in that serial . She had to be so that the hero and heroin ie Jai - Bani can unite in the end. In all Ekta serial the odd one in the Love Triangle becomes Evil so that the other two can unite. See Tanya of KSBKBT Evil so that Karan-Nandini unite and latest is the above eg of Kasam Se. So My guess is if Samar and Gauri have to lead a happy life togethere in future then Kaya has to be made evil so that Samar gets over her. Else he should have got over Kaya after she got married to Shashank. Yet he kept on saying " I love Kaya" .... Even when he agreed to marry Gauri for Kartavya sake.
See Kaya's life - loved Vivan , lost him to Aastha because of Gauri, loved Samar but was married to Shashank. Afterwards everyone - Dada,Dadi, Mahen Alok wanted Samar and Gauri to marry. No one cared or bothered about Kaya . Did they ? All such conditions change Ekta Maiya actors and make them Evil. Even Kaya mite have felt neglected and joined Shashank. She agreed immediatly to live with Shashank when Gauri asked her to ? No questions ? No arguments ? And she was in the Kapoor House before Nikhila's death . May be she was with Shashank. Shashank phoned and informed Kaya about Gauri running with the papers and their conversation was heard by Nikhila so Kaya stabbed Nikhila , closed the light and rest we know what happed .. May be Nikhila was trying to tell Samar to Save Gauri and he misunderstood.
If Kaya was not with Shashank then she should have been with father Alok and must know about Shivangi-Gauri.. If she is not with Father then she must be with Shashank only