Was Geeta working for Tamraj Kilvish?
What even suggest that?
Geeta was just a superhero love interest like Lois Lane or Mary Jane. To be frank, most of Shaktimaan lore is parallel to Superman:
Superman and Shaktimaan both are superheroes with an alter-ego working with the news agency and have a girlfriend who is an aspiring reporter. Coincident?
Secondly, till we see her last, Geeta Vishwas never showed any sign of evil motives and the franchise is on hold for now after the film Hamara Hero Shaktimaan and the animated show is a spinoff with new settings and relations.
If you still doubt Geeta then we have to doubt every superhero love interest and even sidekicks for no apparent reason.