Anita was positive until the last scene of the previous season.
Also regarding Shesha, adaa never said if her character would turn positive or negative in the beginning, they only said that she will play a naagin who turned negative mid way. It was the articles that kept positioning adaa as the vamp.
Coming to DSDT, didn’t jasmine later take over as the main and end up with the male lead towards the end of the story as per the info given online? That sure is a skill or say talent for a so called ‘side kick’ which is why I highly doubt she is a vamp or would play one.
You can go ahead and check the DSDT forum to know what was Teni Vamp or Lead.
After the lead actress exited still teni wasn't able to become the lead that says a lot abt her character teni and her acting