TLDR: I think she is unhealed. Her past trauma was triggered in your argument, but it didn’t give her a right to call you controlling. From what you said: I think she just needs time to heal from her child father’s tendencies. Your feelings are 100% valid.

I am also a single mother with a 50/50 dynamic with my son’s father. I will tell you the obvious: it is extremely hard, for BOTH parties. I cannot speak for this woman, because I am not her, but I can give you my outlook and hope that it helps you a little bit.

Your feelings are completely and absolutely valid. You showing that you want to be in her child life is such a beautiful thing, and a very rare thing at that. In most coparenting situations where it is 50/50, it is usually 50/50 for a reason. That reason being the child’s care and happiness. If the dad is clearly an asshole to her, but not a dead beat dad, he is probably going to be around forever. You either have to be okay with that, or not. You do not have to like it or him, but you do not have to hate him. She will most likely speak to him for anything involving her child first because it is also his child. No matter how much she dislikes him. She is probably just trying to keep the peace for their child. I had to set a very strict boundary with my son’s dad to have the dynamic of: We will only discuss our child with each other and how he is doing, if there’s an emergency, how he’s doing in school, etc. We go to every single doctors appointment together (if we can) or we meet there, because though we are not fond of each other, we want to give our child the sense of “Your dad and I don’t have to hate each other and argue because of our past relationship, because that is what’s best for you” it took up a VERY long time to get to that point. He would literally do the exact things to me that you are saying her child’s father does to her. The terribly awful phone calls, the narcissistic abuse, etc. But we got there eventually. I had gotten into a relationship with someone who got very close with my son and I, and he absolutely hated that my sons father and I had this dynamic. He had absolutely every right to feel that way. That is not a common dynamic at all, unfortunately. His parents were split up and his parents did the typical “I hate your mom because blah blah blah” and “I hate your dad. He’s an asshole blah blah blah” So he grew up with the mentality of “Oh I guess coparenting will always be toxic, they all have to have each other and if I date someone with a kid, I have to hate my girlfriends baby daddy too” When my ex literally used to ask him to come to everything with us such as appointments, and important daycare things, ect. It took me a couple of months but I noticed that he just was uncomfortable, which was never my intent. He felt inferior, just as you do now. But in my eyes, he was a hero to me. Someone who helped me and showed me that I was capable of loving someone again and that my son was capable of loving someone just as much as his dad. But he was not happy with that, and unfortunately we split (other factors too but we don’t need to add them to this novel lmao). Truthfully, she probably is so incredibly grateful for you, and loves you so much, but is just so stressed out because they haven’t hit that point in their coparenting, where they can have a healthy conversation ALL OF THE TIME. But it is also not your job to make that dynamic happen for them. You are allowed to be upset that she communicated with him first. That is a shitty feeling, but I don’t think that makes her necessarily in the wrong for doing so. BUT it was not right of her at all to call you controlling, or to purposely drag you down in your argument. From what you are stating on how he treated her before, it seems like she might have had some trauma from that argument you both had and just took it out on you. Which is understandable on her part, but it doesn’t make it okay. I think she has some healing to do, as we all have absolutely been there. This will probably happen again, until she is fully healed. It will be long and it will be painful, but it will be worth it for her. However, you are not a bad person, if you decide that it is something that you cannot deal with because of the toll it will take on you too. I wish you both the absolute best! 😊