I used to move my job but now I’m confused

The company I work for takes care of its employees, the pay is good and management has been great. Until now. My significant other works at the same company and has been having issues with a co-worker who happens to be a close friend of the manager who oversees the whole department.

Said co-worker is a bit controlling and got upset when my significant other didn’t want to participate on a dynamic that only brought him trouble. Said dynamic is not part of the workplace procedures, just something this co-worker thought was beneficial.

Anyway, his rage toward my significant other grew so much that she would be rude to me - we don’t work directly together.

As I mentioned earlier, this coworker is friends with the manager who completely backs him up and believes everything this coworker tells him. He is constantly accusing my significant other of being rude and dismissive and I’m afraid that I am collateral damage.

I have been a good employee, I’ve gotten promotions and really good reviews, but now I feel something shifted. I had a good work relationship with the manager but lately I’ve been getting the cold shoulder and I feel uncomfortable. I don’t want to change jobs because the pay is good and my direct supervisor is good. I hate that I have to go to work with a sense of drag and a pit in my stomach and my gut tells me I will be overlooked for upcoming opportunities due to the conflict my significant other’s coworker has created.