Will I never learn?

My husband works with a woman that I dislike. I think she is manipulative, ambitious, and self-serving. There have been instances when she’s been very dismissive of me and he hasn’t really stood up for me. And since she’s an employee of his, I haven’t felt I can stand up for myself. We have had many, many fights over her. There is a wealth of negative thoughts and a belief system in myself that he will side with her/work over me.

So the last couple weeks I’ve been trying to not have a relationship manual. I’ve been trying to manage my emotions. But last night, it’s like something goaded me into poking the beast. I think things have been going better for me and with my husband, so for some sick reason I felt the need to test to see if my husband would back me. So I brought up something I heard her talking about at a birthday party for his business partner. He was out of town, but I went, knowing she would be there but believing I could handle my emotions regarding her. She brought up an incident with a co-worker in which she talked like she was a supervisor of this person and how she had to take over an interaction, which seemed wrong to me because the co-worker is the manager for her customer service department, and she is the marketing person.

C- I asked him “Is she that person’s boss?” He responded that she wasn’t.
T – I will explain her description of her interaction with the other person and he will finally see things from my perspective and back me up.
A – explained what happened, won’t let subject drop, dig in deeper and deeper into why I don’t think she’s nice, act petty, bring up examples of past interactions when I felt he didn’t back me up, said I just want to feel like we are on the same team
R – I prevent us from having a nice evening and feel worse than before bringing it up.

I don’t think this is a good model. But I really want to figure out how to get to the bottom of this situation because it’s killing me.