What are we supposed to do if our union rep is friends with management?

Apparently, our union rep has been talking hours to our supervisor. The supervisor who has been sneaky for years, and is manipulative. She has harrassed me blatantly, but has also created a false workman's comp case etc. The list goes on. She is a manipulative person....

What are we supposed to do? Our union rep was originally supposed to help my coworkers with back pay. It's been more than 6 months of working on this.

The all of a sudden our rep calls, "Yea I'm not helping you work with that. You can talk too (previous reps name) about that."

Already our rep switched sides!

I talked to my rep about sexual harrassment that I had experienced with that supervisor.This was something i didn't want to do, but needed to. It put me in an uncomfortable spot. But now, I'm so worried that she has gossiped about me to our rep.