I don’t see where she controlled you by telling you who you can and cannot talk to. She told you how she felt about you talking to the cousin, but I didn’t see where she said not to?
You are spewing resentment all over her. I did that for a little while myself in the beginning. You know where that got me? Absolutely no where except swimming in my own pain and resentment. And that leaks on over to the kids and doesn’t allow for coparenting or effective parallel parenting. When I stopped, it was me who felt much better. I wasn’t punishing my ex. He didn’t care one way or another. I was punishing myself and my daughter.
I learned it doesn’t matter who’s “fault” it was or “who started it” just ask yourself what’s best for your kids. Calm peaceful communication regarding the children? Focus on that as your goal.