even though she never was my supervisor, she acted like it.
Did you clear this up with your actual supervisor? I’ve had plenty of cases where I’ve been given work by people not my supervisor, but my supervisor wanted me to help the other person out. And that no one wanted to hear your side of the story seems to suggest that this could be the case. You seem to be focusing on the popularity of your coworker rather than giving information on the reporting structure of your company.
It sounds like you aren’t happy in your given role at work, so you might as well leave. However, it seems like there may have been a different understanding to what your job is than what you thought it was.