Stats: 20's, dating this one for 1.5 years, 5'9, 155lbs lean, was spinning plates until I decided I prefer to focus on this ltr. Enjoying the process.
Read Book of Pook, NMMNG, WISNIFG, reading TMM

I've got to a point where I feel I'm pretty confident with my abilities and knowledge, but sometimes I still have a hard time implementing the right tools. Recently I had an event like this, and I'd like to learn from it and prevent mistakes in the future.

I'm on a work trip for a couple weeks, so I talked with her on the phone one evening. Mid call she raised her voice on me about something minor, so I checked her, "listen, next time I'll not be ok with you talking to me like that, and it's not the first time either". I have laid boundaries before but never this one, and this time she went bonkers. She said that she didn't even raise her voice, and my tone was very aggressive and disrespectful. Yeah sure, I fogged, don't care. She got hurt, demanded an apology. Still fogged, told her "well if you didn't raise your voice and I'm not mad either, there's no problem here". I wasn't able to get us to move on with fogging and am. Eventually I decided to end the call when she insisted on an apology, saying she won't be able to sleep now cuz she's sad.

Next day I figured we're past that nonsense but turns out that's where the tricky part starts: "we need to talk and solve this".
I say ok sure, we can have a calm talk. The problem is that in situations like this any amused mastery or flirting is not really accepted, she's genuinely stubbornly wants to seriously talk about it, no joking around.
I told her that I stand on what I've said. It's an important boundary and it's sad that she's hurt but I stand behind my words. It didn't solve this, because she "has to hear an apology for hurting her with my attitude, even if I don't take my words back".
I feel like this is the turning point where I felt like it's total freestyle, no regular tools here, just me and my frame.
It kept going on, I fogged a lot but she straight up asked me question after question so I answered them like I would to my little sister, explaining how different people can have different opinions and it's ok if she's hurt, shit happens, but again it didn't help. Eventually after a long talk I told her "If that makes any sense to you then yes I didn't mean to hurt you and I apologize for that you but I stand firmly behind what I've said", Only then she got calm and turned back to her cute self.

Tbh it feels awful. At first I wasn't even remotely invested in this nonsense and somewhere along the "solve this" bullshit I lost myself and probably was deering, even interrupted her to talk. In some way it's also like I reinforced her nonsense at the end with the apology, even tough I didn't go back on my words. At that point it felt really butthurt to stand my ground when she asks why can't I just say the words I apologize if it'll make her feel better, even if I don't regret my actions, just to say it so she can be at peace. It felt like the most responsible teen is now a 5 year old.

Maybe I should've just refused to talk about all of this (verbal intercourse is optional) and disappear for a few days, but in my view if the convo is calm and normal I'm there to have it, why not.

Feels like something is missing for me, I would love to hear some feedback and personal input to learn from the situation.