She’s not really tricked into being evil. She’s tricked into taking the final step, but she has serious issues to start with and she’d have never taken the final step if she wasn’t on that path to start with. The big thing it really sets up is that she had the option to not be evil.
I was under the impression that she had the propensity of being evil, then moved towards it. It might have had something to do with her tight leather pants.