Maybe it wasn't just her, I think it was the both of us. I have this coworker. We started on the same day and somehow hated each other immediately and cultivated making each other's life difficult to the point HR noticed and transferred us to the opposite ends of the company for good. A few years later she was sent to my department, we didn't speak a word. Then her team was suffering an extreme staff shortage so my boss sent me to help "I need someone who gets a lot of work done in no time, so that's your part". She was the only one remaining in the team, and it turned out she was really capable and we had a similar approach to work. Since then we at least said hello.

A little while later I was the one with the staff shortage and guess what happens - she was permanently transferred to my team, and as my boss. From that day we shared the same room for 39 hours a week. Given the story told you may not be surprised I didn't mind that much anymore, also workload was way too big for antics. I needed her as she was capable and there, she needed me as I knew every customer and procedure.

When the biggest chunk was done and work allowed it, I was looking out of the window. She stood next to me. And we started to talk. And talk. And talk. Maybe one hour straight. We apologized, realized how stupid we had both been and promised that this would never happen again. From that day on, we became inseparable at work and later on even insisted to be kept in one office when another shortage came up. We basically told our boss if he split us he wouldn't get 2*50 % of our joint capacity, but far less.

We don't work together anymore, but we are still on very friendly terms with each other.